Biocatalytic process unit

Abstract

A biocatalytic process unit is described. The biocatalytic process unit comprises, in normal flow sequence: one or more process feed lines; a break tank fluidly connected to the one or more process feed lines; and a biocatalytic reaction vessel fluidly connected to the break tank. The biocatalytic process unit further comprises an interlock system configured to isolate the break tank from the one or more process feed lines in response to backflow from the biocatalytic reaction vessel to the break tank. Also described is a control method for the biocatalytic process unit, the control method comprising detecting backflow from the biocatalytic reaction vessel to the break tank; and subsequently actuating the interlock system to isolate the break tank from the one or more process feed lines. Also described is a microbial fermentation of a microorganism in the biocatalytic process unit.

Description

[0001] Biocatalytic Process Unit

[0002] Field of the Invention

[0003] The present invention relates to a biocatalytic process unit and a method of controlling such a biocatalytic process unit.

[0004] Background

[0005] Chemical processes, such as biocatalytic processes (e.g. fermentations), may involve the handling of flammable substances (e.g. gases), such as hydrogen (H2), carbon monoxide (CO), and methane (CH4). By way of example, a gas fermentation may consume a mixture of CO, CO2 and H2 as a substrate, and thus the process unit may comprise a hydrogen feed to a fermentation vessel.

[0006] Flammable gases can produce an explosion when they are ignited while at a concentration (typically in a mixture with air) between their lower explosive limit and upper explosive limit, which are specific to the flammable gas, or mixture of flammable gases, present.

[0007] Where a biocatalytic process involves the handling of flammable substances, the equipment configured to be used in the presence of such substances during normal operation, or which may be used in the presence of such substances under abnormal operation, are required to be safety certified for such use, as leaks of flammable gases can result in explosive mixtures in the vicinity of that equipment. The EU directive describing the minimum safety requirements for equipment used in explosive atmospheres (i.e. work areas that contain flammable gases, mists or vapours, or combustible dusts) is the ATEX 114 “equipment” directive 2014 / 34 / EU.

[0008] Typically, all equipment within a biocatalytic process unit handling flammable substances would be ATEX- compliant, even where only a part of that biocatalytic process unit contains flammable substances during normal operation.

[0009] The present invention has been devised in light of the above considerations.

[0010] Summary of the Invention

[0011] At its most general, in a first aspect, the present invention relates to a chemical process unit comprising, in normal flow sequence: one or more process feed lines; a break tank fluidly connected to the one or more process feed lines; and a pressure vessel (e.g. a reactor pressure vessel) fluidly connected to the break tank; wherein the chemical process unit further comprises an interlock system configured to isolate the break tank from the one or more process feed lines in response to backflow from the pressure vessel to the break tank. Being able to isolate the break tank from the process feed lines in response to backflow prevents backflow of liquid and gas into the process feed lines and other process equipment upstream of the break tank, and further prevents the process feed lines and other process equipment upstream of the break tank from being exposed to the pressure vessel operating pressure. Where the pressure vessel contains flammable substances, such as flammable gases (e.g. hydrogen gas, carbon monoxide, methane) or flammable liquids (e.g. ethanol, methanol, acetone, butanone, isoprene) that are capable of being vaporised (e.g. at typical operating temperatures for the process), and which are able to provide explosive gas mixtures when mixed with air in the required ratio (i.e. between the lower explosive limit and upper explosive limit of the flammable gas / vapour), the ability to prevent backflow of such gases and / or liquids to process equipment upstream of break tank means that process equipment (e.g. the process feed lines) upstream of the break tank does not need to be ATEX- compliant (nor ATEX-certified). Non-ATEX-compliant equipment is typically smaller, and uses less material, than ATEX-compliant equipment. Moreover, non-ATEX-compliant / certified equipment requires less frequent inspection compared to ATEX-compliant / certified equipment, meaning that longer process runs are possible. Moreover, process safety can be improved, as the number of possible failure points that would result in release of flammable gas and / or liquid is reduced.

[0012] The ability to avoid exposing the process equipment upstream of the pressure vessel to the pressure vessel’s operating pressure also allows for lower design pressures for this process equipment. This reduces the material use and the size of said process equipment, and improves process safety, as the number of possible failure points that would result in high-pressure failure of process equipment is reduced.

[0013] Moreover, such a chemical process unit provides a simple and robust system, in terms of safety, operability and mechanical issues in process equipment that can result from backflow.

[0014] Where reference is made to ATEX or the ATEX 114 “equipment” directive 2014 / 34 / EU herein, it may be understood that the present invention is equally applicable where equivalent international or national regulations I directives apply. By way of example, in the USA, the NFPA 70 standard may apply, or internationally, the IEC 60079-11 :2023 (or national variants thereof) may apply.

[0015] More specifically, the invention according to the first aspect may be applied to a biocatalytic process unit (i.e. a type of chemical process unit) comprising, in normal flow sequence: one or more process feed lines; a break tank fluidly connected to the one or more process feed lines; and a biocatalytic reaction vessel (i.e. a type of pressure vessel) fluidly connected to the break tank; wherein the biocatalytic process unit further comprises an interlock system configured to isolate the break tank from the one or more process feed lines in response to backflow from the biocatalytic reaction vessel to the break tank. The first aspect is particularly suited to application to a biocatalytic process unit, as the process feed lines in a biocatalytic process unit are typically not all at an elevated pressure (e.g. may be substantially below the pressure of the biocatalytic reaction vessel), and typically do not all contain flammable gases and / or flammable liquids.

[0016] A biocatalytic process may be understood to be a process making use of biologically active components to catalyse chemical reactions. Biocatalysis includes processes occurring in cell-free, fully in vitro environments, and fermentation-mediated processes in living cell cultures. The biocatalytic process unit may be a fermentation process unit or a cell-free, in vitro enzymatic process unit. Where the biocatalytic process is a fermentation process, the biocatalytic reaction vessel may be a fermentation vessel. Based on the above-described normal flow sequence, it can be understood that the break tank may be positioned intermediate the process feed line(s) and the biocatalytic reaction vessel, such that material in the process feed line(s) passes through the break tank to reach the biocatalytic reaction vessel. It can also be understood that the one or more process feed lines may be fluidly connected to the break tank in parallel with each other.

[0017] The interior volume of the biocatalytic reaction vessel may be at least 10 times greater than the interior volume of the break tank. This not only reduces the material use and the size of the break tank, but also means that the pressure of the break tank is more responsive to backflow from the biocatalytic reaction vessel, i.e. for the same flowrate of material backflow from the biocatalytic reaction vessel to the break tank, the smaller the break tank interior volume, the greater the rate of pressure increase in the break tank. This can allow for earlier detection of backflow to the break tank (e.g. where backflow is detected based on the pressure in the break tank). Preferably, the interior volume of the biocatalytic reaction vessel is at least 25 times greater than the interior volume of the break tank, e.g. around, or greater than, 50 times the interior volume of the break tank. This allows for even earlier detection of backflow to the break tank. The biocatalytic process unit may be an industrial scale process unit. The interior volume of the biocatalytic reaction vessel may be at least 1 m3, at least 5 m3, at least 50 m3, at least 150 m3, or at least 250 m3.

[0018] The break tank may also be referred to as a pressure isolation tank, a gas barrier feed tank, or an explosion barrier tank.

[0019] The biocatalytic process unit may be a biocatalytic process unit configured to handle flammable substances, such as flammable liquids and / or flammable gases. The biocatalytic process unit may be configured to supply a flammable gas or flammable liquid as a substrate. The biocatalytic process unit may be configured for a fermentation (i.e. the biocatalytic process unit may be a fermentation process unit) that produces a flammable gas or flammable liquid as a product. The above process unit is particularly suited to such fermentations, as the interlock system can be used to prevent flammable substances provided to, or produced in, the biocatalytic reaction vessel from reaching components of the process unit that do not handle such substances under normal operating conditions.

[0020] The fermentation process unit may be a gas fermentation process unit, for example, a gas fermentation process unit configured for use in fermentation of CO and / or CO2, optionally in the presence of H2 (e.g. a flue-gas or syngas composition) and, optionally, trace gases. The above process unit is particularly suited to gas fermentation, especially syngas or flue-gas fermentation, as the interlock system can be used to prevent gas provided to the fermentation vessel as a substrate for the fermentation from reaching components of the process unit that do not handle such gases under normal operating conditions.

[0021] The biocatalytic process unit (e.g. a control system within the biocatalytic process unit) may be configured to actively control a liquid level in the break tank. By way of example, the biocatalytic process unit may comprise a biocatalytic reaction vessel feed pump disposed on a line between (i.e. fluidly connecting) the break tank and the biocatalytic reaction vessel, and the biocatalytic process unit may be configured such that a pump speed of the biocatalytic reaction vessel feed pump is controlled based on the liquid level in the break tank (e.g. by a level controller provided on the break tank and connected to the biocatalytic reaction vessel feed pump). Additionally, or alternatively, the biocatalytic process unit may comprise a break tank feed pump disposed on each process feed line, and the biocatalytic process unit may be configured such that a pump speed of each break tank feed pump is controlled based on the liquid level in the break tank. However, a temperature of the break tank (e.g. the temperature of the contents of the break tank) may not be actively controlled or controllable. By way of example, the break tank may not comprise a temperature control element (e.g. a heating or cooling element) or a temperature control jacket. The break tank may not comprise a temperature sensor. That is, it can be understood that the break tank is not a fermentation vessel (i.e. the break tank is not configured to support the growth of microorganisms therein). The break tank may allow for mixing of the material from the one or more process feed lines prior to said material reaching the biocatalytic reaction vessel. The break tank may not comprise a mixer, agitator and / or sparger. The break tank may not comprise a dissolved oxygen sensor and / or a pH sensor.

[0022] One or more of the process feed lines (e.g. each process feed line) may be liquid process feed lines, i.e. process feed lines may be configured to provide liquid streams to the biocatalytic reaction vessel (via the break tank). The one or more process feed lines may be selected from the group consisting of: an inert gas (e.g. nitrogen) purge line; a fermentation nutrient line; a fermentation medium recycle line; a process water line; and one or more pH control lines (e.g. for adding acid and / or base to the biocatalytic reaction vessel for pH control). The one or more process feed lines may not be configured to contain (or may not be suitable for containing) flammable material.

[0023] The biocatalytic reaction vessel may be pressure rated for a maximum absolute working pressure (MAWP) of greater than or equal to 0.15 MPaG (1 .5 barg) at 60°C. The biocatalytic reaction vessel may be pressure rated for a MAWP of less than or equal to 2.0 MPaG (20 barg) at 60°C. For example, the biocatalytic reaction vessel may be pressure rated for a MAWP of less than or equal to 1 .6 MPaG (16 barg) at 60°C, or less than or equal to 1 .2 MPaG (12 barg) at 60°C and / or may be pressure rated for a MAWP greater than or equal to 0.8 MPaG (8 barg) at 60°C, or greater than or equal to 0.6 MPaG (6 barg) at 60°C, or greater than or equal to 0.3 MPaG (3 barg). In one embodiment, the biocatalytic reaction vessel may be pressure rated for a MAWP of less than or equal to 1 .6 MPaG (16 barg) at 60°C and greater than or equal to 0.8 MPaG (8 barg) at 60°C. In another embodiment, the biocatalytic reaction vessel may be pressure rated for a MAWP of less than or equal to 1 .2 MPaG (12 barg) at 60°C and greater than or equal to 0.6 MPaG (6 barg) at 60°C. The present invention can allow the process feed lines and / or break tank (and / or any other process equipment upstream of the break tank in normal flow sequence) not to be pressure rated to the same, elevated, MAWP as the biocatalytic reaction vessel; that is, the MAWP of the biocatalytic reaction vessel may be greater than the MAWP of the process feed lines (and / or any other process equipment upstream of the break tank in normal flow sequence). The design pressure of the biocatalytic reaction vessel may be less than or equal to 1 .0 MPaG (10 barg), e.g. around 0.5 MPaG (5 barg). The design pressure of the biocatalytic reaction vessel may be greater than or equal to 0.15 MPaG (1.5 barg) and / or less than or equal to 0.4 MPaG (4 barg). The one or more process feed lines may be pressure rated for a MAWP of less than or equal to 0.3 MPaG at 60°C. For example, the process feed lines may be pressure rated for a MAWP of greater than 0 MPaG at 60°C and less than or equal to 0.3 MPaG at 60°C, e.g. 0.1 MPaG at 60°C. Typically, the design pressure of the process feed lines is around atmospheric pressure (i.e. 0 MPaG). As a result of the present invention, the process feed lines can be pressure rated for such a MAWP without risk of them being exposed to a higher pressure, e.g. the pressure of the biocatalytic reaction vessel. This reduces the material use and the size of said process equipment.

[0024] The break tank may be pressure rated for a MAWP of less than or equal to 0.3 MPaG at 60°C. For example, the break tank may be pressure rated for a MAWP of greater than 0 MPaG at 60°C and less than or equal to 0.3 MPaG at 60°C, e.g. 0.2 MPaG at 60°C. Typically, the design pressure of the break tank is above atmospheric pressure and below the design pressure of the biocatalytic reaction vessel (e.g. less than or equal to 0.2 MPaG, such as about 0.125 MPaG). As a result of the present invention, the break tank can be pressure rated for such a MAWP without risk of it being exposed to a higher pressure, e.g. the pressure of the biocatalytic reaction vessel. This reduces the material use and the size of said process equipment. The break tank being pressure rated for such a MAWP may be further facilitated by the biocatalytic process unit further comprising a vent line, the vent line fluidly connected to (e.g. directly connected to) the break tank and / or the biocatalytic reaction vessel. The vent line (e.g. a safety valve disposed on the vent line) may be configured to be closed during normal operation of the biocatalytic process unit and may be configured to open during abnormal operation of the biocatalytic process unit. For example, the biocatalytic process unit may be configured such that the vent line (e.g. the safety valve) opens in response to backflow from the biocatalytic reaction vessel (e.g. due to an increase in pressure in the break tank, or due to an increase in pressure in the biocatalytic reaction vessel that causes the backflow) and / or following isolation of the break tank from the one or more process feed lines. The vent line is configured for venting (i.e. removing) gas from the break tank and / or the biocatalytic reaction vessel. In this way, the process feed lines can be isolated from the break tank to prevent the process feed lines from being exposed to overpressure (e.g. due to backflow thereto) and the break tank and / or biocatalytic reaction vessel can be vented to prevent the break tank from being exposed to overpressure.

[0025] The break tank and biocatalytic reaction vessel may be ATEX-compliant (and optionally, ATEX-certified). The one or more process feed lines may be not ATEX-compliant (and / or not ATEX-certified). “ATEX- compliant” may be defined as being compliant with the ATEX 114 Equipment Directive 2014 / 34 / EU. The configuration of the interlock system in the biocatalytic process unit allows such a separation of the process equipment of the process unit into an ATEX-compliant / certified section and a non-ATEX- compliant / certified section. Non-ATEX-compliant equipment is typically smaller, and uses less material, than ATEX-compliant equipment. Moreover, non-ATEX-compliant / certified equipment does not require as frequent inspection as ATEX-compliant / certified equipment, meaning that longer process runs are possible. The biocatalytic process unit may comprise a break tank feed pump disposed on each process feed line, and each break tank feed pump may be non-ATEX-compliant (and / or not ATEX-certified). The biocatalytic process unit may comprise a biocatalytic reaction vessel feed pump disposed on a line between (i.e. fluidly connecting) the break tank and the biocatalytic reaction vessel, and the biocatalytic reaction vessel feed pump may be ATEX-compliant (and, optionally, ATEX certified). More broadly, any one or more pieces of process equipment upstream of the break tank may be non-ATEX-compliant (and / or not ATEX-certified), and process equipment downstream of the break tank may be ATEX- compliant (and, optionally, ATEX certified).

[0026] The biocatalytic process unit may comprise a check valve disposed on the line between the break tank and the biocatalytic reaction vessel (e.g. downstream of the biocatalytic reaction vessel feed pump). The check valve may be configured to only pass flow in the direction from the break tank to the biocatalytic reaction vessel.

[0027] The interlock system may comprise a sensor configured to detect backflow from the biocatalytic reaction vessel to the break tank; and a controller configured to isolate the break tank from the one or more process feed lines in response to backflow detection by the sensor. By way of example, the sensor may transmit a reading to the controller, and the controller may isolate the break tank from the one or more process feed lines in response to the reading (e.g. where the reading exceeds or falls below a threshold value, or where the pressure increases or decreases by a certain percentage from a design or steady state operating pressure). The sensor may comprise a pressure sensor configured to measure pressure in a headspace of the break tank; a pressure sensor configured to measure pressure in a headspace of the biocatalytic reaction vessel; or a flow sensor disposed on a line between (i.e. fluidly connecting) the break tank and the biocatalytic reaction vessel. The flow sensor may be configured to measure a flow rate along the line from the biocatalytic reaction vessel to the break tank. Such sensors are able to provide reliable detection of backflow from the biocatalytic reaction vessel to the break tank. A pressure sensor configured to measure pressure in the headspace of the break tank may provide earlier detection of backflow than a pressure sensor configured to measure pressure in the headspace of the biocatalytic reaction vessel, for example, in the typical case of the break tank internal volume being less than the biocatalytic reaction vessel internal volume. A pressure sensor (configured to measure break tank or biocatalytic reaction vessel pressure) may be more resistant to contamination / fouling than the flow sensor disposed on the line between the break tank and biocatalytic reaction vessel. In some embodiments, the interlock system may comprise a plurality of sensors configured to detect backflow from the biocatalytic reaction vessel to the break tank (e.g. a plurality of the aforementioned sensors). In this way, redundancy in the interlock system may be provided; in particular, by providing a plurality of sensors, each sensor configured to measure a different parameter (e.g. break tank pressure, biocatalytic reaction vessel pressure, or flow rate), the interlock system is provided with redundancy in such a way that a failure mode of one sensor is less likely to also affect the reading of another sensor.

[0028] The break tank may comprise a valve on an inlet of each process feed line into the break tank. The interlock system may be configured to isolate the break tank from the one or more process feed lines by shutting each valve. The valves on the inlet of each process feed line into the break tank may be provided in a manifold. By way of example, where the interlock system comprises a controller, the controller may be configured to shut each valve to isolate the break tank from the one or more process feed lines, e.g. in response to backflow detection by the sensor.

[0029] The biocatalytic process unit may further comprise a vent line, the vent line fluidly connected to (e.g. directly connected to) the break tank and / or the biocatalytic reaction vessel. By way of example, the vent line may be configured to be able to vent gas (directly) from the headspace of the break tank and / or the biocatalytic reaction vessel. In this way, pressure relief can be provided to the break tank and / or the biocatalytic reaction vessel. A safety valve may be disposed on the vent line. Where the vent line is fluidly connected to the break tank, the safety valve and interlock system may be configured such that, in response to backflow from the biocatalytic reaction vessel to the break tank, the safety valve actuates after isolation of the break tank from the one or more process feed lines.

[0030] Where the safety valve is disposed on the vent line (or a branch thereof) connected to the biocatalytic reaction vessel to vent gas from the headspace thereof, the safety valve may be configured to open at a pressure less than or equal to the MAWP of the biocatalytic reaction vessel. Where the safety valve is disposed on the vent line (or a branch thereof) connected to the break tank to vent gas from the headspace thereof, the safety valve may be configured to open at a pressure less than or equal to the MAWP of the break tank. For example, where the interlock system is configured to detect backflow using a pressure sensor configured to measure pressure in the headspace of the break tank, the break tank pressure at which backflow is determined to have occurred (and at which the interlock system is configured to isolate the break tank from the process feed lines) may be less than or equal to the pressure at which the safety valve on the vent line connected to the break tank is configured to open. In this way, the biocatalytic process unit not only acts to prevent backflow of flammable gases into the process feed lines due to a buildup of pressure and / or a low liquid level in the biocatalytic reaction vessel, but also acts to be able to vent gas from the biocatalytic reaction vessel to release the pressure buildup causing the backflow and / or vent gas that has flowed back from the biocatalytic reaction vessel to the break tank out of the break tank. By the vent line being fluidly connected to the break tank to vent gas from the headspace thereof, it is possible for the break tank to be rated to a MAWP lower than the MAWP of the biocatalytic reaction vessel. Where the vent line is connected to both the break tank and the biocatalytic reaction vessel, the biocatalytic process unit may comprise a first safety valve disposed on a first branch of the vent line directly connected to the break tank, and a second safety valve disposed on a second branch of the vent line directly connected to the biocatalytic reaction vessel. The first and second branches of the vent line may join downstream of the safety valves.

[0031] The biocatalytic process unit may further comprise a biocatalytic reaction vessel feed pump disposed on a line between the break tank and the biocatalytic reaction vessel. The biocatalytic reaction vessel feed pump may be rated to overcome the pressure differential between the break tank pressure and the biocatalytic reaction vessel pressure. In this way, the biocatalytic reaction vessel feed pump is operable to pump liquid from the break tank into the biocatalytic reaction vessel. The biocatalytic reaction vessel feed pump may be pressure rated for a MAWP greater than or equal to the MAWP of the biocatalytic reaction vessel. The biocatalytic process unit may further comprise a gas feed line, the gas feed line fluidly connected to the biocatalytic reaction vessel in parallel to the break tank. The gas feed line may be configured to supply a flammable gas to the biocatalytic reaction vessel. By way of example, the gas feed line may be configured to supply H2, CO, and / or C02to the biocatalytic reaction vessel. In this way the fermentation process unit (biocatalytic process unit) is configured for carrying out gas fermentation, and by fluidly connecting the gas feed line to the fermentation vessel (biocatalytic reaction vessel) in parallel to the break tank, gas supplied by the gas feed line is only able to reach the break tank by backflow from the fermentation vessel to the break tank. Accordingly, the interlock system only needs to be able to isolate the break tank from the process feed lines in response to such backflow to ensure that flammable gases and / or liquids do not reach the process feed lines.

[0032] The biocatalytic process unit may further comprise a break tank feed pump disposed on each process feed line. The break tank feed pump may be configured to pump a liquid supplied by the respective process feed line to the break tank. Where a process feed line is an inert gas purge line, it may not be provided with a break tank feed pump. Instead, the inert gas purge line may be provided with a compressor. That is, the biocatalytic process unit may comprise a break tank feed pump disposed on each process feed line configured to supply liquid to the break tank. The interlock system may be further configured to interlock each break tank feed pump (or compressor, where present) in response to backflow from the biocatalytic reaction vessel to the break tank. The interlock system may be configured to do so simultaneously with, or subsequent to, isolating the break tank from the process feed lines. In this way, the biocatalytic process unit is provided with redundancy for preventing the upstream propagation of flammable gases and / or liquids along the process feed line(s).

[0033] At its most general, in a second aspect, the present invention relates to a control method for a chemical process unit, wherein: the chemical process unit comprises, in normal flow sequence: one or more process feed lines; a break tank fluidly connected to the one or more process feed lines; and a pressure vessel fluidly connected to the break tank; the chemical process unit further comprises an interlock system configured to isolate the break tank from the one or more process feed lines; and the control method comprises: detecting backflow from the pressure vessel to the break tank; and subsequently actuating the interlock system to isolate the break tank from the one or more process feed lines.

[0034] More specifically, the invention according to the second aspect may be applied to a biocatalytic process unit (e.g. a method of controlling a microbial fermentation), wherein: the biocatalytic process unit comprises, in normal flow sequence: one or more process feed lines; a break tank fluidly connected to the one or more process feed lines; and a biocatalytic reaction vessel fluidly connected to the break tank; the biocatalytic process unit further comprises an interlock system configured to isolate the break tank from the one or more process feed lines; and the control method for the biocatalytic process unit comprises: detecting backflow from the biocatalytic reaction vessel to the break tank; and subsequently actuating the interlock system to isolate the break tank from the one or more process feed lines.

[0035] The biocatalytic process unit may be the biocatalytic process unit according to the first aspect. The control method may comprise detecting backflow from the biocatalytic reaction vessel using a sensor. By way of example, the sensor may be configured to measure pressure in a headspace of the break tank.

[0036] Where the biocatalytic process unit further comprises a vent line and a safety valve disposed thereon, the vent line fluidly connected to the break tank and / or the biocatalytic reaction vessel, the control method may further comprise the safety valve opening after detecting backflow from the biocatalytic reaction vessel to the break tank (e.g. a pressure in the break tank indicative of backflow may also be the pressure at which the safety valve opens).

[0037] Where the biocatalytic process unit comprises a break tank feed pump disposed on each process feed line, the control method may further comprise interlocking each break tank feed pump in response to detecting backflow from the biocatalytic reaction vessel to the break tank. The method may comprise interlocking each break tank feed pump simultaneously with, or subsequent to, isolating the break tank from the process feed lines.

[0038] At its most general, in a third aspect, the present invention relates to a chemical process being conducted in a chemical process unit according to the first aspect.

[0039] More specifically, the invention according to the third aspect may be applied as a microbial fermentation of a microorganism in a fermentation process unit according to the first aspect.

[0040] The microbial fermentation may be configured to produce one or more organic acids as the target product. Said one or more organic acids may be selected from the group consisting of acetic acid, butyric acid; propionic acid; lactic acid; succinic acid; pyruvic acid; tartaric acid; iso-butyric acid; hydroxybutyric acid; and hydroxyvaleric acid. Preferably, said one or more organic acids may be selected from the group consisting of acetic acid, butyric acid; propionic acid; lactic acid; and succinic acid. Most preferably, said one or more organic acids consists of acetic acid. In addition, or alternatively, the microbial fermentation may be configured to produce one or more flammable substances (e.g. flammable gases and / or flammable liquids) as the target product, for example, one or more of the substances selected from the group consisting of: ethanol, methanol, butane, acetone, butanol, butanone, and isoprene. The fermentation process unit according to the first aspect in which the microbial fermentation is conducted is particularly well suited to controlling such fermentations such that safer operation of the fermentation is possible without having to make all of the process equipment ATEX-compliant / certified and rated for the maximum pressure in the process unit.

[0041] The microbial fermentation may comprise gas fermentation with an organic acid-producing microorganism in a fermentation broth. The microorganism may be thermophilic. For example, the thermophilic microorganism may be selected from the group consisting of: thermophilic acetogens; thermophilic propionibacteria; thermophilic butyric acid bacteria; thermophilic lactic acid bacteria; thermophilic succinic acid bacteria; and hydrogen oxidising bacteria; thermophilic pyruvic acid bacteria; thermophilic tartaric acid bacteria; thermophilic iso-butyric acid bacteria; thermophilic hydroxybutyric acid bacteria; and thermophilic hydroxyvaleric acid bacteria. Preferably, the thermophilic microorganism may be selected from the group consisting of: thermophilic acetogens; thermophilic propionibacteria; thermophilic butyric acid bacteria; thermophilic lactic acid bacteria; thermophilic succinic acid bacteria; and hydrogen oxidising bacteria.

[0042] Alternatively, the microorganism may be mesophilic. For example, the microorganism may be selected from the group consisting of: mesophilic acetogens; mesophilic propionibacteria; mesophilic butyric acid bacteria; mesophilic lactic acid bacteria; mesophilic succinic acid bacteria; and hydrogen oxidising bacteria; mesophilic pyruvic acid bacteria; mesophilic tartaric acid bacteria; mesophilic iso-butyric acid bacteria; mesophilic hydroxy butyric acid bacteria; and mesophilic hydroxyvaleric acid bacteria. Preferably, the mesophilic microorganism may be selected from the group consisting of: mesophilic acetogens; mesophilic propionibacteria; mesophilic butyric acid bacteria; mesophilic lactic acid bacteria; mesophilic succinic acid bacteria; and hydrogen oxidising bacteria.

[0043] An acetogen may be defined as a microorganism having a metabolism converting CO2 (with H2) or CO into acetyl-coenzyme-A. A propionibacterium may be defined as a microorganism having a metabolism converting CO2 (with H2) or CO into propionyl-coenzyme-A. A butyric acid bacterium may be defined as a microorganism having a metabolism converting CO2 (with H2) or CO into butyryl-coenzyme-A. A lactic acid bacterium may be defined as a microorganism having a metabolism converting CO2 (with H2) or CO into lactyl-coenzyme-A. A succinic acid bacterium may be defined as a microorganism having a metabolism converting CO2 (with H2) or CO into succinyl-coenzyme-A. A hydrogen-oxidising bacterium may be defined as a microorganism having a metabolism capable of using hydrogen as an electron donor. A pyruvic acid bacterium may be defined as a microorganism having a metabolism converting CO2 (with H2) or CO into pyruvyl-coenzyme-A. A tartaric acid bacterium may be defined as a microorganism having a metabolism converting CO2 (with H2) or CO into tartryl-coenzyme-A. An iso-butyric acid bacterium may be defined as a microorganism having a metabolism converting CO2 (with H2) or CO into isobutyryl-coenzyme-A. A hydroxybutyric acid bacterium may be defined as a microorganism having a metabolism converting CO2 (with H2) or CO into hydroxybutyryl-coenzyme-A. A hydroxyvaleric acid bacterium may be defined as a microorganism having a metabolism converting CO2 (with H2) or CO into hydroxyvaleryl-coenzyme-A.

[0044] In one example, a butyric acid bacterium may be defined as a bacterium capable of producing butyric acid. A lactic acid bacterium may be defined as a bacterium capable of producing lactic acid. A succinic acid bacterium may be defined as bacterium capable of producing succinic acid. A pyruvic acid bacterium may be defined as a bacterium capable of producing pyruvic acid. A tartaric acid bacterium may be defined as bacterium capable of producing tartaric acid. An iso-butyric acid bacterium may be defined as a bacterium capable of producing iso-butyric acid. A hydroxybutyric acid bacterium may be defined as bacterium capable of producing hydroxybutyric acid. A hydroxyvaleric acid bacterium may be defined as bacterium capable of producing hydroxyvaleric acid. The bacterium may be thermophilic or mesophilic, but preferably is thermophilic.

[0045] The microorganism may be selected from the genera consisting of: Moorella, Thermoanaerobacter, Thermoanaerobacterium, Acetogenum, Carboxydothermus, Clostridium, Butyribacterium, Eubacterium, Pyrococcus, Desulfobacterium, Parageobacillus, Geobacillus and Acetobaterium. In particular, the microorganism may be selected from the group consisting of: Clostridium Ljungdahlii, Clostridium autoethanogenum, Acetogenium kivui, Acetobacterium woodii, Acetoanaerobium noterae, Clostridium aceticum, Butyribacterium methylotrophicum, Clostridium acetobutylicum, Clostridium thermoaceticum, Eubacterium limosum, and Moorella thermoautotrophica. Preferably, the microorganism is Moorella thermoaceticum. Moorella thermoaceticum is known to be capable of producing acetic acid, for example.

[0046] The microbial fermentation may be an industrial scale process. Said industrial scale process may be a fermentation in at least 1 m3scale, at least 5 m3scale, at least 50 m3scale, at least 150 m3scale, or at least 250 m3scale.

[0047] The temperature of the fermentation broth may be above 45°C. Operating at above 45°C can increase the productivity of the thermophilic microorganism whilst inhibiting the growth of mesophilic contaminant microorganisms. The temperature of the fermentation broth may be above 50°C, 55°C, 60°C, or 65°C. The temperature of the fermentation broth may be below 75°C, 70°C, 65°C, 60°C or 55°C. The upper bound of the temperature of the fermentation broth may be set based on the temperature that the organic acid-producing thermophilic microorganism can withstand without being inhibited. The temperature of the fermentation broth may be above 45°C and below 75°C. In one embodiment, the temperature of the fermentation broth is above 55°C and below 65°C. The fermentation process unit according to the first aspect in which the microbial fermentation is conducted is particularly well suited to controlling such fermentations, because at thermophilic temperatures, lower explosive limits for gas mixtures containing flammable gases are lower, and upper explosive limits for such gas mixtures is higher, and the vapour pressure of flammable substances is greater, making the ability to isolate the break tank from the process feed lines in response to backflow even more important in improving the safety of the process.

[0048] Alternatively, the temperature of the fermentation broth may be less than or equal to 45°C. The temperature of the fermentation broth may be above 20°C, for example, between 20°C and 45°C, such as about 37°C. This can facilitate growth of a mesophilic organism.

[0049] The total organic acid productivity may be defined as the productivity of both free acid and dissociated / ionised acid forms of the one or more organic acids. The total organic acid productivity of the microbial fermentation may be greater than or equal to 8 mM / hour, greater than or equal to 12 mM / hour, greater than or equal to 17 mM / hour, greater than or equal to 25 mM / hour, greater than or equal to 33 mM / hour, greater than or equal to 40 mM / hour, or greater than or equal to 50 mM / hour. The total organic acid productivity may be calculated based on the organic acid produced by the microbial fermentation over a time period of 1 hour, 6 hours, 12 hours, 1 day, 2 days or 1 week. Preferably, the productivity may be calculated based on the total organic acid produced by the microbial fermentation over a time period of 12 hours, and / or the total organic acid productivity may be greater than or equal to 33 mM / hour. Free acid may be defined as undissociated acid (i.e. in its protonated form). By way of example, undissociated acetic acid is CH3COOH. The free acid concentration in the fermentation broth may be defined as the sum of the concentrations of one or more acids in their protonated form (i.e. the sum of individual free acid concentrations) in the supernatant of the fermentation broth. The free acid concentration may be the free acid concentration of the one or more organic acids (for example, if no inorganic acid species were present in the fermentation broth).

[0050] The “Maximum Allowable Working Pressure (MAWP)” of a piece of process equipment may be understood as the greatest amount of pressure that the weakest part of the piece of process equipment can handle at a specified design temperature (at 60°C in the case of the present application). “Overpressure” may be understood as a pressure exceeding the MAWP of a piece of process equipment.

[0051] The “design pressure” of a piece of process equipment may be understood as the highest level of pressure the piece of process equipment should be exposed to under normal operating conditions.

[0052] References to pressure values in vessels (e.g. in the break tank, or the biocatalytic reaction vessel), such as the design pressure, may be understood to be references to the pressure in the headspace of such vessels.

[0053] “Active control” of a process variable, or an “actively controlled” process variable, may be understood as control wherein that process variable is the measured variable within a control loop that is compared to a set point value (e.g. to determine an error signal for a controller).

[0054] In the present application, a microorganism being thermophilic may be defined as the microorganism being capable of growing at a temperature above 45°C.

[0055] In the present application, a microorganism being mesophilic may be defined as the microorganism being capable of growing at a temperature greater than or equal to 20°C and less than or equal to 45°C.

[0056] The invention includes the combination of the aspects and preferred features of the first, second and third aspects described above, except where such a combination is clearly impermissible or expressly avoided.

[0057] Although optional features of the first and second aspect have been set out in relation to a fermentation process unit and a control method for a fermentation process unit, these optional features are equally applicable to the first and second aspects at their most general (i.e. in relation to a chemical process unit more broadly).

[0058] Summary of the Figures

[0059] Figure 1 is a process flow diagram of a fermentation process unit; and

[0060] Figure 2 is a flowchart illustrating steps a control method for the fermentation process unit illustrated in Figure 1 .

[0061] Detailed Description of the Invention

[0062] Aspects and embodiments of the present disclosure will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art. Figure 1 is a process flow diagram of a fermentation process unit (i.e. a type of biocatalytic process unit). The fermentation process unit comprises, in normal flow sequence, a plurality of process feed lines 1a, 1 b, 1c, 1d, a break tank 2 fluidly connected to the one or more process feed lines 1a - 1d, and a fermentation vessel 3 fluidly connected to the break tank 2.

[0063] The fermentation process unit is configured for gas fermentation of flammable gases (e.g. containing H2 and / or CO), e.g. fermentation of syngas by acetogenic bacteria. The gas is supplied to the fermentation vessel 3 by a gas feed line 8. The gas fermentation also has a plurality of liquid feedstocks to be fed to the fermentation vessel, including nutrients, recycled media (e.g. media recovered through downstream product separation processes) and water. Although Figure 1 only illustrates three liquid feedstocks, the present invention is not limited in this regard, and further liquid feedstocks may be fed to the fermentation vessel via process feed lines in the fermentation process unit, as illustrated with respect to process feed lines 1a - 1c in Figure 1. The nutrients are supplied in a fermentation nutrient line 1a, the recycled media is supplied in a fermentation medium recycle line 1 b, and the process water is supplied in a process water line 1 c. The liquid feedstocks are pumped along their respective process feed lines 1a - 1c by respective break tank feed pumps 6a - 6c disposed on said process feed lines 1a - 1c. A process feed line 1d for delivering nitrogen gas for purging the fermentation process unit with inert gas is also present. Rather than feeding directly into the fermentation vessel 3, the process feed lines 1 a - 1d feed into the break tank 2 and are then subsequently fed from the break tank 2 to the fermentation vessel 3 by a fermentation vessel feed pump 7 disposed on a line between the break tank 2 and the fermentation vessel 3. As illustrated in Figure 1 , the gas feed line 8 providing the flammable gas(es) that are the substrate for the fermentation is connected to the fermentation vessel 3 in parallel to the process feed lines 1a - 1d and break tank 2.

[0064] As illustrated in Figure 1 , the line from the fermentation vessel feed pump 7 to the fermentation vessel 3 is configured to feed liquid from the break tank 2 into the fermentation vessel 3 proximate the top of the fermentation vessel 3, whilst the gas feed line 8 is configured to feed gas into the fermentation vessel proximate the bottom of the fermentation vessel 3 (in an alternative configuration, the liquid feed from the break tank 2 into the fermentation vessel 3 may be proximate the bottom of the fermentation vessel and / or the gas feed line 8 is configured to feed gas into the fermentation vessel 3 proximate the top of the fermentation vessel 3) .

[0065] Backflow from the fermentation vessel 3 to the break tank 2 may occur under certain abnormal conditions. A prerequisite for backflow to occur is that the check valve disposed on the line between the break tank 2 and the fermentation vessel 3 is faulty, allowing fluid to flow in both directions and thereby also backwards into the break tank 2. Subsequently, where pressure in the fermentation vessel 3 (e.g. in the headspace of the fermentation vessel 3 when the line from the break tank 2 thereto is connected to the top of the fermentation vessel 3) exceeds the pressure in the line between the break tank 2 and fermentation vessel, backflow will occur. Such a pressure gradient may occur, for example, due to: a) emptying of the break tank, b) a fault in the fermentation vessel feed pump 7, or c) a leakage in the line between the break tank 2 and fermentation vessel 3. Flammable gases may flow backwards from the fermentation vessel 3 to the break tank 2 in three different forms: over-pressurised gas from the headspace may flow backwards into the break tank 2, gas trapped within a foamy fermentation broth may be driven backwards into the break tank 2, or dissolved gas within the liquid in the fermentation vessel 3 may be transported into the break tank 2 due to liquid backflow.

[0066] Consequently, the fermentation process unit further comprises an interlock system that is configured to isolate the break tank 2 from the one or more process feed lines 1a - 1d in response to backflow (e.g. of gas) from the fermentation vessel 3 to the break tank 2. In this way, further backflow of flammable gases upstream of the break tank 2 into the process feed lines 1a - 1d is prevented.

[0067] Specifically, Figure 1 illustrates a manifold 9 that forms part of the break tank 2 and is actuatable by the interlock system to isolate the break tank 2 from the process feed lines 1a - 1d. The manifold 9 comprises a plurality of valves (not illustrated), each valve provided on an inlet of each process feed line 1a - 1d into the break tank 2. The interlock system is configured to shut each valve in order to isolate the break tank 2 from the process feed lines 1a - 1d. The interlock system in Figure 1 further comprises a plurality of sensors configured to detect backflow from the fermentation vessel to the break tank; in particular, the interlock system comprises a first pressure sensor 4c configured to measure the pressure in the headspace of the fermentation vessel 3, a second pressure sensor 4d configured to measure the pressure in the headspace of the break tank 2, and a flow sensor 4b disposed on the line between the break tank and the fermentation vessel. Backflow from the fermentation vessel 3 to the break tank 2 can be detected by a drop in the pressure measured by the first pressure sensor 4c, an increase in pressure measured by the second pressure sensor 4d, or a measurement by the flow sensor 4b that indicates that the direction of flow is from the fermentation vessel 3 to the break tank 2, rather than the flow direction under normal operation (i.e. from the break tank 2 to the fermentation vessel 3). The interlock system comprising a plurality of sensors provides redundancy within the system. The primary sensor used by the interlock system is the second pressure sensor 4d, provided as a pressure transmitter device (PT). The interlock system further comprises a controller 4a, provided as a pressure-indicator-controller (PIC) device, and to which the second pressure sensor 4d is connected to transmit its reading thereto. The controller 4a is connected to the interlock such as to be able to shut the valves therein. The first pressure sensor 4c and flow sensor 4b are provided as pressure transmitter (PT) device and flow transmitter (FT) devices, respectively, and are connected to the controller 4a to transmit their readings thereto. Although not illustrated in Figure 1 , the controller 4a may also be connected to the break tank feed pumps 6a - 6c and may be configured to interlock each break tank feed pump in response to backflow from the fermentation vessel 3 to the break tank 2.

[0068] The fermentation process unit further comprises a level controller 4e, provided as a level-indicator- controller (LIC) device, connected to the break tank 2 and configured to measure the liquid level therein. The level controller 4e is also connected to the fermentation vessel feed pump 7 and can set the pump speed of the fermentation vessel feed pump 7 to provide control of the liquid level in the break tank 2. Alternatively, the level controller 4e could be connected to the break tank feed pumps 6a - 6c and configured to set the pump speed of the break tank feed pumps 6a - 6c to provide control of the liquid level in the break tank 2.

[0069] The fermentation process unit illustrated in Figure 1 further comprises a vent line 5 connected to both the break tank 2 and the fermentation vessel 3. A first branch of the vent line 5 is directly connected to the break tank 2 and has a first safety valve 5a disposed thereon, and a second branch of the vent line 5 is directly connected to the fermentation vessel 3 and has a second safety valve 5b disposed thereon. The branches of the vent line 5 join downstream of the safety valves 5a, 5b. In this way, the vent line 5 is configured to be able to vent gas from the headspace of both the break tank 2 and the fermentation vessel 3, such that neither vessel exceeds its respective maximum absolute working pressure (MAWP). The first safety valve 5a is configured to open at a pressure less than or equal to the MAWP of the break tank 2, which itself is typically less than or equal to 0.3 MPaG at 60°C, whilst the second safety valve 5b is configured to open at a pressure less than or equal to the MAWP of the fermentation vessel 3, which itself is typically greater than or equal to 0.5 MPaG (5 barg) at 60°C and less than or equal to 2.0 MPaG (20 barg) at 60°C. In this way, the fermentation process unit not only acts to prevent backflow of flammable gases into the process feed lines 1a - 1d due to a buildup of pressure in the fermentation vessel 3, but also acts to be able to vent gas from the fermentation vessel 3 to release the pressure buildup causing the backflow and / or vent gas that has flowed backwards from the fermentation vessel 3 out of the break tank 2.

[0070] The connection of the vent line 5 to the break tank 2 to be able to vent gas from the headspace thereof also allows the break tank to be rated to a MAWP lower than the MAWP of the fermentation vessel. The first safety valve 5a is configured to open at a pressure between the break tank pressure reading from the second pressure sensor 4d at which the controller 4a is configured to isolate the break tank 2 from the process feed lines 1a - 1d and the MAWP of the break tank 2.

[0071] Similarly, because the interlock system 2 isolates the process feed lines 1a - 1d from the break tank 2 at a break tank pressure below the MAWP of the break tank 2 and the first safety valve 5a is configured to open at a pressure less than or equal to the MAWP of the break tank 2, the process feed lines 1a - 1d and the break tank feed pumps 6a - 6c disposed thereon can also be pressure rated for a MAWP less than the MAWP of the fermentation vessel 3 (e.g. they can be pressure rated for a MAWP equal to the MAWP of the break tank 2 or the opening pressure of the first safety valve 5a).

[0072] The above-described configuration of the fermentation process unit is such that backflow of flammable gases from the fermentation vessel 3 to the break tank 2 can only propagate as far as the break tank 2, and that flammable gases cannot backflow upstream of the break tank 2 (upstream of manifold 9), i.e. into the process feed lines 1a - 1d. This means that the process equipment upstream of the break tank 2 (e.g. the process feed lines 1a - 1d and the break tank feed pumps 6a - 6c) does not need to be compliant with, and / or certified for, ATEX 114 Equipment Directive 2014 / 34 / EU (“ATEX-compliant”), whereas the break tank 2 and process equipment downstream thereof (e.g. the fermentation vessel 3) do need to be ATEX-compliant and, optionally, ATEX certified. This is illustrated in Figure 1 , where the fermentation process unit is separated into a non-ATEX-compliant / certified zone 10 and an ATEX- compliant / certified zone 20.

[0073] Figure 2 is a flowchart illustrating steps a control method for the fermentation process unit illustrated in Figure 1 .

[0074] At step S100, backflow from the fermentation vessel 3 to the break tank 2 is detected. As discussed above, in the case of the fermentation process unit in Figure 1 , backflow is primarily detected using the second pressure sensor 4d configured to measure the pressure in the break tank 2, but can also be detected by the first pressure sensor 4c and / or the flow sensor 4b.

[0075] Subsequently, at step S200, the break tank 2 is isolated from the process feed lines 6a - 6d by the interlock system; the controller 4a acts to shut the valves in the manifold 9 in response to the second pressure sensor reading exceeding a threshold pressure.

[0076] If backflow from the fermentation vessel 3 to the break tank 2 continues after isolation of the process feed lines 1a - 1d, the pressure in the break tank 2 will continue to rise, and at step S300, the first safety valve 5a and / or the second safety valve 5b open to relieve pressure from the break tank 2 and / or fermentation vessel 3.

[0077] The flowchart in Figure 2 further comprises step S400 of interlocking the break tank feed pumps 6a - 6c on the process feed lines 1a - 1c in response to detecting backflow from the fermentation vessel 3 to the break tank 2. As illustrated in Figure 2, step S400 may be conducted after step S200 of isolating the break tank 2 from the process feed lines 1a - 1c, or may be conducted in parallel to step S200, as illustrated by the dashed arrow from S100 to S400 in Figure 2.

[0078] ***

[0079] The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

[0080] While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

[0081] For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations.

[0082] Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described. Throughout this specification, including the claims which follow, unless the context requires otherwise, the word “comprise” and “include”, and variations such as “comprises”, “comprising”, and “including” will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” one particular value, and / or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it will be understood that the particular value forms another embodiment. The term “about” in relation to a numerical value is optional and means for example + / - 10%.

Claims

Claims:1 . A biocatalytic process unit comprising, in normal flow sequence: one or more process feed lines; a break tank fluidly connected to the one or more process feed lines; and a biocatalytic reaction vessel fluidly connected to the break tank; wherein the biocatalytic process unit further comprises an interlock system configured to isolate the break tank from the one or more process feed lines in response to backflow from the biocatalytic reaction vessel to the break tank.

2. The biocatalytic process unit according to claim 1 , wherein an interior volume of the biocatalytic reaction vessel is at least 10 times greater than an interior volume of the break tank.

3. The biocatalytic process unit according to any preceding claim, wherein the biocatalytic process unit is configured to actively control the liquid level of the break tank.

4. The biocatalytic process unit according to any preceding claim, wherein the temperature in the break tank is not actively controlled.

5. The biocatalytic process unit according to any preceding claim, wherein the biocatalytic reaction vessel is pressure rated for a maximum absolute working pressure of greater than or equal to 0.15 MPaG and less than or equal to 2.0 MPaG.

6. The biocatalytic process unit according to any preceding claim, wherein the one or more process feed lines are pressure rated for a maximum absolute working pressure of less than or equal to 0.3 MPaG.

7. The biocatalytic process unit according to any preceding claim, wherein the break tank is pressure rated for a maximum absolute working pressure of less than or equal to 0.3 MPaG.

8. The biocatalytic process unit according to any preceding claim, wherein the interlock system comprises: a sensor configured to detect backflow from the biocatalytic reaction vessel to the break tank; and a controller configured to isolate the break tank from the one or more process feed lines in response to backflow detection by the sensor.

9. The biocatalytic process unit according to claim 8, wherein the sensor comprises: a pressure sensor configured to measure pressure in a headspace of the break tank; a pressure sensor configured to measure pressure in a headspace of the biocatalytic reaction vessel; and / or a flow sensor disposed on a line between the break tank and the biocatalytic reaction vessel.

10. The biocatalytic process unit according to any preceding claim, wherein:the break tank comprises a valve on an inlet of each process feed line into the break tank; and the interlock system is configured to isolate the break tank from the one or more process feed lines by shutting each said valve.11 . The biocatalytic process unit according to any preceding claim, further comprising a vent line, the vent line fluidly connected to the break tank and / or the biocatalytic reaction vessel.

12. The biocatalytic process unit according to claim 11 , wherein: the vent line is fluidly connected to the break tank; a safety valve is disposed on the vent line; and the safety valve and interlock system are configured such that, in response to backflow from the biocatalytic reaction vessel to the break tank, the safety valve actuates after isolation of the break tank from the one or more process feed lines.

13. The biocatalytic process unit according to any preceding claim, further comprising a biocatalytic reaction vessel feed pump disposed on a line between the break tank and the biocatalytic reaction vessel.

14. The biocatalytic process unit according to any preceding claim, wherein the one or more process feed lines are selected from the group consisting of: an inert gas (e.g. nitrogen) purge line; a fermentation nutrient line; a fermentation medium recycle line; a process water line; a pH control line; and a base line.

15. The biocatalytic process unit according to any preceding claim, further comprising a gas feed line, the gas feed line fluidly connected to the biocatalytic reaction vessel in parallel to the break tank.

16. The biocatalytic process unit according to any preceding claim, wherein: the biocatalytic process unit further comprises a break tank feed pump or compressor disposed on each process feed line; and the interlock system is further configured to interlock each break tank feed pump and compressor in response to backflow from the biocatalytic reaction vessel to the break tank.

17. The biocatalytic process unit according to any preceding claim, wherein the biocatalytic process unit is a fermentation process unit.

18. A control method for a biocatalytic process unit, wherein: the biocatalytic process unit comprises, in normal flow sequence: one or more process feed lines;a break tank fluidly connected to the one or more process feed lines; and a biocatalytic reaction vessel fluidly connected to the break tank; the biocatalytic process unit further comprises an interlock system configured to isolate the break tank from the one or more process feed lines; and the control method comprises: detecting backflow from the biocatalytic reaction vessel to the break tank; and subsequently actuating the interlock system to isolate the break tank from the one or more process feed lines.

19. The control method according to claim 18, wherein the control method comprises detecting backflow from the biocatalytic reaction vessel using a pressure sensor configured to measure pressure in a headspace of the break tank.

20. The control method according to claim 18 or 19, wherein: the fermentation process unit further comprises a vent line and a safety valve disposed thereon, the vent line fluidly connected to the break tank and / or the biocatalytic reaction vessel; and the control method further comprises the safety valve opening after detecting backflow from the biocatalytic reaction vessel to the break tank.

21. The control method according to any of claims 18 to 20, wherein: the biocatalytic process unit further comprises a break tank feed pump disposed on each process feed line; and the control method further comprises interlocking each break tank feed pump in response to detecting backflow from the biocatalytic reaction vessel to the break tank.

22. A microbial fermentation of a microorganism in a biocatalytic process unit according to any of claims 1 to 17.

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