A production system for preparing lactic acid by fermenting kitchen waste with Rhizopus oryzae

Abstract

The present invention relates to the technical field of lactic acid preparation, and discloses a production system for preparing lactic acid by fermenting kitchen waste with Rhizopus oryzae. The system comprises at least three reactors, the top of the reactor is provided with an air duct, a neutralizer duct, and a culture solution duct, the bottom of the reactor is provided with a carbon source duct and an output duct, the neutralizer duct and the air duct have a junction pipe with the tail end of the culture solution duct; a centrifuge, the inlet end of the centrifuge is connected to the outlet end of the reactor; a filter, the inlet end of the filter is connected to the outlet end of the centrifuge; and an esterification device, the inlet end of the esterification device is connected to the outlet end of the filter. The production system reduces the breakage of filamentous fungi, increases the gas content, and improves the production efficiency of filamentous fungi.

Description

Technical Field

[0001] The invention relates to the technical field of lactic acid preparation and discloses a production system for preparing lactic acid by fermenting kitchen waste with Rhizopus oryzae. Background Art

[0002] Kitchen waste refers to the waste generated in residents' daily life and food processing, catering services, unit catering and other activities. These wastes contain extremely high moisture and organic matter, are easily perishable and produce foul odors, but can be converted into new resources after proper treatment and processing. Kitchen waste pretreatment methods include acid or alkaline treatment, enzymatic hydrolysis, microwave or ultrasonic treatment, repeated freeze-thaw cycles, high pressure treatment, thermal treatment and micro-aeration treatment. Enzymatic hydrolysis of food waste is superior to other methods because it is cost-effective and has relatively low energy requirements, milder reaction conditions, lower production of toxic byproducts and higher efficacy. Enzymes help convert large molecular solids in food waste into soluble small molecules.

[0003] In today's basic scientific research on biological science, Rhizopus oryzae has been widely studied as a host cell for L-lactic acid (LLA) production, and it has been finally confirmed to be one of the most efficient hosts currently. Rhizopus oryzae belongs to the category of filamentous fungi. This filamentous fungus can effectively secrete hydrolases to use organic waste as a carbon source for its own glycolysis. Under the action of Rhizopus oryzae, the organic matter in kitchen waste is fermented under aerobic conditions to produce lactic acid. However, in general systems for producing lactic acid, the mycelium is easily broken and the production efficiency is low. Summary of the invention

[0004] In view of the shortcomings of the prior art mentioned above, the purpose of the present invention is to provide a production system for preparing lactic acid by fermenting kitchen waste with Rhizopus oryzae. In view of the above situation, in order to solve the defects of the prior art, the purpose of the present invention is to provide a method for producing lactic acid by fermenting kitchen waste with Rhizopus oryzae, reducing the breakage of filamentous fungi and increasing the gas content.

[0005] In order to solve the above technical problems, the present invention provides the following technical solution: a production system for preparing lactic acid by fermenting kitchen waste with Rhizopus oryzae, the production system comprising:

[0006] At least three reactors, wherein an air pipeline, a neutralizer pipeline, and a culture solution pipeline are arranged at the top of the reactor, a carbon source pipeline and an output pipeline are arranged at the bottom of the reactor, and the neutralizer pipeline and the air pipeline have a junction pipe at the tail end of the culture solution pipeline;

[0007] a centrifuge, wherein the inlet end of the centrifuge is connected to the outlet end of the reactor;

[0008] A filter, wherein the inlet end of the filter is connected to the outlet end of the centrifuge;

[0009] and an esterification device, wherein the inlet end of the esterification device is communicated with the outlet end of the filter.

[0010] Preferably, a delivery pump is connected in series to the carbon source pipeline and the output pipeline.

[0011] More optimally, a vibration anti-blocking device is provided on the intersection pipe.

[0012] More optimally, a mechanical stirrer is provided in the reactor, and the mechanical stirrer comprises a stirring shaft, a stirring paddle and a bearing, and the stirring paddle is provided with a blade.

[0013] More optimally, the reactor is provided with a motor, and the output end of the motor is connected to the stirring shaft.

[0014] More optimally, the bottom of the reactor is a rectangular kettle, and a baffle with an inclined angle is provided at the bottom of the reactor, and the angle a between the baffle and the midline of the bottom of the reactor is 45°.

[0015] More optimally, the stirring paddle includes a first stirring paddle, a second stirring paddle and a third stirring paddle, the first stirring paddle is arranged at the uppermost layer, the second stirring paddle is arranged below the first stirring paddle, and the third stirring paddle is arranged below the second stirring paddle.

[0016] More optimally, an annular gas distributor is provided in the reactor, and the center of the annular gas distributor is connected to the bearing and is located above the first stirring paddle.

[0017] More optimally, the first stirring impeller and the second stirring impeller are four-fold blade impellers, and the third stirring impeller is a six-straight blade disc turbine impeller.

[0018] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0019] 1. Multiple reactors can be used to achieve greater throughput.

[0020] 2. The stirring paddles are set with different types and diameters according to the upper and lower layers to reduce the breakage rate of mycelium.

[0021] 3. Set up baffles and annular gas distributors to increase the gas content in the reactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is the equipment flow chart of the production system of the present invention;

[0023] Figure 2 It is a schematic diagram of the structure of the reactor of the present invention;

[0024] Figure 3 This is a schematic diagram of a six-straight-blade disc turbine propeller of the present invention;

[0025] Figure 4 It is a schematic diagram of the four-fold blade paddle of the present invention. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] See also Figure 1 The present invention provides a production system for preparing lactic acid by fermenting kitchen waste with Rhizopus oryzae. The production system comprises various units connected in series by pipelines, and the pipelines can be used to transport materials.

[0028] like Figure 1 As shown, the production system may include at least three reactors 1, and the reactor 1 is a sterile container that can be used to control process parameters, which can ensure that the process parameters in the isolated environment, such as pH, oxygen saturation and temperature, reach the optimal conditions. The volume of the reactor 1 is 7L. The top of the reactor 1 is provided with an air duct 2, a neutralizer duct 3, and a culture fluid duct 4. The air duct 2, the neutralizer duct 3 and the culture fluid duct 4 can be arranged in parallel. Further, the top of the reactor 1 is provided with a first input port 14, and the first input port 14 connects the air duct 2, the neutralizer duct 3 and the culture fluid duct 4. In some embodiments, the neutralizer 3 duct and the air duct 2 have a junction pipe 15 at the tail end of the culture fluid duct 4. The bottom of the reactor 1 is provided with a carbon source duct 5 and an output duct 6, and a delivery pump is also connected in series on the carbon source duct 5 and the output duct 6. The carbon source of the present invention passes through the carbon source pipeline 5 and enters the second input port 16 from the bottom of the reactor 1, and can be more evenly distributed in the fermentation medium, which is very important for ensuring the uniformity of microbial growth and metabolic activity. Adding from the bottom can reduce contact with air, thereby reducing the risk of oxidation and avoiding foam. During the fermentation process, adding a carbon source may cause the generation of foam, and adding from the bottom can reduce the formation of foam because it can reduce the agitation of air.

[0029] The intersection pipe 15 may be provided with a vibration anti-blocking device 7 at the outer wall at the top of the reactor 1, which effectively eliminates the blockage caused by internal friction, deliquescence, component segregation and the like by high-frequency vibration and impact force, so that the culture solution is smoothly discharged from the pipeline into the reactor 1. The reactor 1 can optimize the reproduction rate of Rhizopus oryzae under constant optimal fermentation conditions to maximize the lactic acid production capacity. The production system may include a centrifuge 8, the inlet end of the centrifuge 8 is connected to the outlet end of the reactor 1. The production system may include a filter 9, the inlet end of the filter 9 is connected to the outlet end of the centrifuge 8. The production system may include an esterification device 10, the inlet end of the esterification device 10 is connected to the outlet end of the filter 9. The concentrations of the culture solution components are: glucose 120-135 g / L, (NH4)2SO4 0.9-1.5 g / L, KH2PO4 0.45-0.65 g / L, MgSO4*7H2O0.45-0.65 g / L, ZnSO4*7H2O 0.04-0.07 g / L, peptone 4-5 g / L, urea 1.2-2.2 g / L, yeast extract 5.5-6.5 g / L, and FeCl3 0.005-0.011 g / L.

[0030] like Figure 2 As shown, the reactor 1 is provided with a motor 12 which can provide power for the mechanical agitator 11 .

[0031] like Figure 2 As shown, the reactor 1 is provided with a mechanical stirrer 11, and the mechanical stirrer 11 is connected to the motor 12. The reactor 1 is usually ventilated and stirred to increase the oxygen dissolution to meet the metabolic needs of the internal microorganisms. The internal fermentation liquid is stirred by the mechanical stirrer 11, so that the air introduced and the fermentation liquid are mixed evenly. Stirring can promote the dissolution of oxygen and make the gas and the fermentation liquid contact evenly, thereby ensuring the growth, metabolism and reproduction of the microorganisms.

[0032] like Figure 2 As shown, the mechanical stirrer 11 includes a stirring shaft 111 , a stirring paddle 112 and a bearing 113 . The output end of the motor 2 is connected to the stirring shaft 111 , and the stirring paddle 112 is provided with a blade 114 .

[0033] like Figure 2As shown, the reactor 1 adopts a low shear design, the stirring paddle 112 includes a first stirring paddle 115, a second stirring paddle 116 and a third stirring paddle 117, the first stirring paddle 115 is arranged at the top layer, the second stirring paddle 116 is arranged below the first stirring paddle 115, the third stirring paddle 117 is arranged below the second stirring paddle 116, the diameter of the first stirring paddle 115 is smaller than the diameters of the second stirring paddle 116 and the third stirring paddle 117, and the diameter of the second stirring paddle 116 is equal to the diameter of the third stirring paddle 117. The intersection pipe 15 extends below the third stirring paddle 117 after entering the reactor 1, and the heights of each stirring paddle 112 are consistent.

[0034] like Figure 2 As shown, the reactor 1 is provided with an annular gas distributor 14, the center of which is connected to the bearing 113 and is located above the first stirring paddle 115, and its function is to evenly distribute the gas over the entire cross section, and is used in conjunction with the stirring paddle 112 to improve the dissolution efficiency of oxygen.

[0035] The gas holdup in the local area of ​​the flow field of the reactor 1 is low, and the low gas holdup near the top stirring paddle is due to the presence of the stirring paddle 112. Reducing the diameter of the upper stirring paddle helps to increase the gas holdup nearby. In order to solve the problem of low gas holdup at the bottom of the reactor 1, the bottom of the reactor 1 is a rectangular kettle, and a baffle 13 with a certain inclination angle is provided at the bottom of the reactor 1. The angle a between the baffle 13 and the midline of the bottom of the reactor 1 is 45°, so as to enhance the mixing effect and prevent dead corners of the fluid.

[0036] like Figure 3 and Figure 4 As shown, the first stirring paddle 115 and the second stirring paddle 116 (axial flow stirring paddle) are four-fold blade paddles, and the third stirring paddle 117 (radial flow stirring paddle) is a six-straight blade disc turbine paddle. The six-straight blade disc turbine paddle has a strong radial discharge capacity and shear effect. The shearing action and radial dispersion capacity provided by the blades 114 are broken into many small bubbles and dispersed to various areas of the reactor 1 along with the liquid circulation, making the gas dispersion more stable and uniform, reducing gas waste and power consumption. The four-fold blade paddle can provide effective axial circulation for the flow field in the reactor 1. Since filamentous bacteria are relatively fragile, if the shear force is not appropriate, it may affect the morphological changes and growth rate of the microorganisms, causing irreversible damage to them, and directly affecting cell growth and products.

[0037] like Figure 1As shown, the fermentation in the reactor 1 is carried out at 29-35°C, accompanied by an empty bed flow rate of 0.7-1cm / s (1vvm of sterile air). During the fermentation process, the pH value will decrease due to the increase in the content of lactic acid in the production system. Therefore, a neutralizer ((NH2)2CO-(NH4)HCO3-NH3·H2O) will be added to the reactor 1 through a pipeline. The neutralizer can increase the pH value of the culture solution to maintain the optimal pH value for the growth of Rhizopus oryzae. At the same time, the neutralizer can react with lactic acid to form new compounds. For example, the ammonia in the neutralizer reacts with lactic acid to form ammonium lactate, which facilitates the subsequent purification of lactic acid.

[0038] like Figure 1 As shown, after the Rhizopus oryzae in the culture solution and the carbon source in the kitchen waste are fully reacted, they enter the centrifuge 8 through the pipeline. The specific model of the centrifuge 8 may be CWL900-M, which is used to separate liquid and solid particles or a mixture of liquid and liquid in the mixture.

[0039] like Figure 1 As shown, after centrifugation, the mixture is transported to the filter 9 through a pipeline, which can specifically be a biological fermentation filter. The principle of the filter is pressure filtration, which can filter the liquid after centrifugation more finely to obtain a supernatant without cells or cell wall fragments.

[0040] like Figure 1 As shown, the supernatant is transported to the esterification device 10 through a pipeline. The esterification device 10 can be heated and pressurized. When the supernatant is heated to 80°C, ammonia is collected. Then, under the condition of continuously removing water and ammonia, n-butanol is added to carry out an esterification reaction of ammonium lactate and n-butanol. The reaction temperature is between 100-130°C and the reaction is carried out at a pressure of 250-275 mmHg for 10-12 hours. The generated n-butyl lactate releases L-lactic acid through hydrolysis.

[0041] Evaluation: Liquid culture medium was added to the reactor 1, and Rhizopus oryzae was inoculated (the initial spore count was about 1x107), and the mechanical stirrer 1 was turned on at a speed of 900 rpm. The culture was carried out at 25°C to 30°C. After 20 hours, a large number of hyphae could be observed by naked eyes in the reactor 1. After the speed reached 900 rpm, the hyphae of the cultivated filamentous fungi were still relatively intact through microscopic observation, and there was no agglomeration phenomenon. If each blade was replaced with three vertical rectangular paddles, the stirring rate would reach 300 to 500 rpm at most, and the hyphae of the fungus would be more broken.

[0042] Conclusion: In the reactor 1, two blades of different shapes are combined and cooperated with each other, the possibility of filamentous fungi getting stuck in the blades is reduced, and the possibility of mycelium being cut off is extremely low, which greatly improves the production efficiency of filamentous fungi.

[0043] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0044] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A production system for preparing lactic acid by fermenting kitchen waste with Rhizopus oryzae, characterized in that: The production system comprises: At least three reactors, wherein an air pipeline, a neutralizer pipeline, and a culture solution pipeline are arranged at the top of the reactor, a carbon source pipeline and an output pipeline are arranged at the bottom of the reactor, and the neutralizer pipeline and the air pipeline have a junction pipe at the tail end of the culture solution pipeline; a centrifuge, wherein the inlet end of the centrifuge is connected to the outlet end of the reactor; A filter, wherein the inlet end of the filter is connected to the outlet end of the centrifuge; and an esterification device, wherein the inlet end of the esterification device is communicated with the outlet end of the filter.

2. The production system according to claim 1, characterized in that: A delivery pump is connected in series on the carbon source pipeline and the output pipeline.

3. The production system according to claim 1, characterized in that: The intersection pipe is provided with a vibration anti-blocking device.

4. The production system according to claim 1, characterized in that: The reactor is provided with a mechanical stirrer, which comprises a stirring shaft, a stirring paddle and a bearing, and the stirring paddle is provided with a blade.

5. The production system according to claim 4, characterized in that: The reactor is provided with a motor, and the output end of the motor is connected to the stirring shaft.

6. The production system according to claim 1, characterized in that: The bottom of the reactor is a rectangular kettle, and a baffle with an inclined angle is arranged at the bottom of the reactor. The angle a between the baffle and the midline of the bottom of the reactor is 45°.

7. The production system according to claim 4, characterized in that: The stirring paddle includes a first stirring paddle, a second stirring paddle and a third stirring paddle. The first stirring paddle is arranged at the uppermost layer, the second stirring paddle is arranged below the first stirring paddle, and the third stirring paddle is arranged below the second stirring paddle.

8. The production system according to claim 1, characterized in that: An annular gas distributor is arranged in the reactor, and the center of the annular gas distributor is connected to the bearing and is located above the first stirring paddle.

9. The production system according to claim 8, characterized in that: The first stirring impeller and the second stirring impeller are four-fold blade impellers, and the third stirring impeller is a six-straight blade disc turbine impeller.

Images