Extraction process of polyhydroxyalkanoates (PHA) from PHA-rich mixed culture waste activated sludge (WAS) in a continuous mode reactor system using low cost acid recovery method

Abstract

The present invention discloses a novel engineered continuous mode extraction process of Poly hydroxy alkanoates (PHA) from PHA-rich mixed culture waste activated sludge (WAS) in a Continuous Mode Reactor system (Figure 1). The said dewatered PHA rich sludge (101) is first subjected to acid treatment in acid mixing tank (102) at 5% w / v ratio enabling proper mixing with 3.5% (v / v) diluted Sulphuric Acid (H2SO4) solution. Acid digestion is conducted in the oil bath (107) at a specific temperature within the range of 8O0C to 90oC maintaining the hydraulic retention time HRT in the acid digester for 6 hours. Then at (120) alkali mixing tank (0.5) N NaOH solution was used to elevate a specific pH within the range of 9.5 - 10.5. After water wash, the extract is treated at hypocloride treatment tank (129). The spent acid is transferred for recycling to acid mixing tank (102) and the spent alkali (127) is transferred for recycling to the alkali mixing tank (120) for further reuse. This process reduces the usage of acid and alkali, thereby, making it cost effective and eco-friendly.

Description

[0001] Extraction Process of Polyhydroxyalkanoates (PHA) from PHA-rich mixed culture waste activated sludge (WAS) in a Continuous Mode Reactor system using low cost acid recovery method

[0002] FIELD OF THE INVENTION:

[0003] The present invention relates to process of extraction of Polyhydroxyalkanoates (PHA) from waste activated sludge (WAS) in a Continuous Mode Reactor system using low cost acid recovery method.

[0004] BACKGROUND OF THE INVENTION:

[0005] One of the biggest threats to our planet earth is the environmental pollution caused by continuous piling of plastic waste in land and water. Therefore, we have witnessed tremendous development in recent years in the use of biodegradable polymers to combat concerns over constant plastic waste accumulation. Today, researchers have developed bioplastic alternatives for almost every single conventional plastic material and corresponding application is being inspected. The most prominent polymers are polylactic acid (PLA), PHA (Polyhydroxyalkanoates), PAs (polyamides) etc. who will show promising production capacities in the next 5 years. The global bioplastics production volume will rise from 2.18 million tonnes in 2023 to estimated 7.43 million tonnes at the end of 2028 as per EUBP Market Data Report 2023.

[0006] PHAs are the biodegradable bioplastics that can successfully replace conventional petrochemical plastics due to their similar material properties. The natural polymers PHA is an assembly of biodegradable polyesters of varied chain length. The polymeric unit pf PHAs can be denoted by formulae: wherein ‘x’ generally ranges from 1 to 5 and n is the polymer chain length. These are produced inside a wide range of microorganisms owing to intracellular carbon and energy storage. Accumulation of PHA granules is guided by the survival mechanism of the bacteria itself. For this reason prompt extraction process is needed to lyse the organism and produce PHA granules.

[0007] In current development of industrial practices, the use of mixed microbial cultures or MMCs is important for various bioprocesses. In industrial research, production of PHAs is a recognized example of MMC application. PHA-rich mixed culture waste activated sludge utilisation in PHA production using renewable resources from wastes (as a substitute of fossil fuels) as carbon source has the potential to reduce production cost.

[0008] Current industrial practice is production of PHA from pure-culture and based on refined feedstock with sterile cultivation settings - these conditions essentially increase the PHA production cost to larger extent.

[0009] Indian Patent no. 288052 by one of the inventors of the instant application, Dr. Partha Chakravarty discloses an integrated system of PHA biomass production from dairy waste water, at laboratory pilot scale. The process relates to a continuous reactor system for the production of polyhydroxybutyrate (PHB), which is one of its kinds in PHA family, comprised mainly of an anaerobic acidogenic reactor, a PHB synthesis reactor and an activated sludge reactor. Each reactor is followed by respective clarifiers. The reactor system performs the functions of conversion of organics present in raw effluent into volatile fatty acids (VFA) in anaerobic acidophilic reactor, production of polyhydroxyalkanoates from the fatty acids in PHB reactor and generation of fresh sludge for the PHB reactor and treatment of residual organics in the wastewater to meet the pollution discharge standards in the Activated Sludge Process (ASP) reactor. The process employed a step of regular chloroform extraction, which is associated with disadvantages. However, for industrial viability we proceed with acid extraction in the present invention instead of the chloroform use. Other recent examples of attempts on PHA productions from mixed culture system are with municipal wastewater treatment facility, food-processing waste streams and municipal solid waste etc.

[0010] Most importantly, to achieve the target of replacing the conventional plastics, it is necessary to reduce PHA production costs which is otherwise 7 to 10 times higher. Till date almost 50% of the total PHA production cost mounts from the recovery and purification process. That is why the process of extraction of PHA from cell biomass are determining step for this bioplastic production in a cost-effective and environment-friendly manner. Limiting the use of halogenated solvents, specifically chloroform are essentials for industrial process development. Use of acid and base as lysing step of biomass is thus a promising technique in PHA recovery process. Laboratory scale research has been done by Lopez-Abelairas et. al. [M. Lopez-Abelairas, M. Garcia-Torreiro, T. Lu-Chau, J.M. Lema, A. Steinbiichel, Comparison of several methods for the separation of poly(3 -hydroxybutyrate) from Cupriavidus necator Hl 6 cultures, Biochemical Engineering Journal, Volume 93, 2015, Pages 250-259] on acid-base extraction of PHA polymer which are chemically viable for industrial use. The chemical lysis method reported by them has been chosen, to build the present invention, a novel engineered continuous mode pilot process for extraction of PHA polymer from PHA-rich mixed culture waste activated sludge (WAS).

[0011] The present invention is a novel ‘engineered continuous mode reactor system’ process employing acid digestion of the bacterial biomass for the effective extraction of PHA bioplastic. The novelty lies in the (a) reactor stream design (b) first time continuous mode engineering in PHA extraction instead of batch mode (c) reporting optimised condition for industrial production plant (d) achievement of more than 50% yield from biomass in industrial mode continuous reactor system (e) industry ready and cost saving due to the use of continuous mode design.

[0012] OBJECTIVES OF THE INVENTION:

[0013] The objective of the present invention is to provide an optimised engineered process involving continuous mode reactor train for extraction of Polyhydroxyalkanoates (PHA) employing acid lysing method from the host biomass, which is generated from agro-based wastewater treatment plant (ETP).

[0014] Another objective of the present invention is to provide a novel process for reducing the PHA extraction cost over other extraction processes in an efficient manner employing a designed continuous yield mode instead of batch mode.

[0015] Further objective of the present invention is to provide a user-friendly integration in a continuous mode operation of a wastewater treatment plant designed to use activated sludge process in producing PHA.

[0016] SUMMARY OF THE INVENTION:

[0017] The present invention is directed to an engineered continuous mode extraction process of Polyhydroxyalkanoates (PHA) from the host biomass, generated from agro-based wastewater treatment processes, in a continuous mode reactor train integrated within a continuous mode PHA production from agro based wastewater treatment process (Patent no. 288052). In this designed process, sulphuric acid of low concentration is used for cell lysis at optimized temperature at a specific optimized retention time followed by alkali treatment and subsequent hypochlorite treatment. This process attains the objective of reducing the PHA extraction cost over other extraction processes in an efficient manner on a continuous yield mode. Process feasibility is demonstrated in its operating ease while integrating in a continuous mode operation of a wastewater treatment plant designed to use activated sludge process in producing PHA. The cell debris after PHA extraction is free from any toxicity / pathogenic activities due to acid digestion of cells.

[0018] BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:

[0019] The foregoing summary, as well as the following detailed description of preferred embodiments, are better understood when read in conjunction with the appended drawings.

[0020] For the purpose of illustrating the invention, exemplary constructions of the invention are shown in the drawings; however, the invention is not limited to the specific methods and system disclosed. The following drawings depict:

[0021] Figure 1: A Schematic process flow diagram on continuous mode PHA extraction engineering

[0022] Figure 2: A photographic view of the continuous mode PHA extraction pilot at the industrial site

[0023] DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS:

[0024] The words "comprising," "having," "containing," and "including," and other forms thereof, are intended to be equivalent in meaning and be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items.

[0025] It must also be noted that as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Although any systems and methods similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present invention, the preferred, systems and methods are now described.

[0026] The disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms.

[0027] According to this invention is provided an extraction process of Polyhydroxyalkanoates (PHA) from PHA-rich mixed culture waste activated sludge (WAS) in a Continuous Mode Reactor system comprising of a plurality of reactors and atleast a combination of reactors which are interconnected along the flow of the sludge biomass with digestion and extraction chemical systems, the process comprising the following steps: 1. subjecting PHA rich mixed culture waste activated sludge (WAS) to dewatering to obtain a dewatered PHA rich sludge (101) with minimum 65% moisture content, followed by acid treatment of the sludge in acid mixing tank

[0102] ;

[0028] 2. transferring the mixed acidic biomass through sludge digestion feed pump

[0104] to the sludge digestion tank

[0105] , maintaining a temperature in the range of 80°C to 90°C, preferably 80oC, for lysing of the bacterial cells, and continuously pumping of biomass mixed acid solution to tank (105) to allow overflow of liquid from the tank (105) , said liquid being cooled in a cooling jacket (108) and subjected to sedimentation by gravity settling in the sludge separator (109) or ultrafiltration by Ultra filtration (UF) membrane separation which is also found to be an effective mode of separation;

[0029] 3. allowing the acid digested biomass to settle in the sludge separator (109) and the supernatant spent acidic overflow (110) to enter the transfer tank (112) and therefrom transferred to the acid mixing tank (102) for reuse; while in case of UF membrane separation, spent acid permeate enters the transfer tank (112);

[0030] 4. pumping the lysed biomass separated by sedimentation or by UF membrane, and settled at the sludge separator tank (109) bottom, by the sludge transfer pump (114) to the neutralization tank (116). washing the biomass with water to reduce the residual acid content, transferring the mixture to the centrifuge (118) using the centrifuge feed pump (117), followed by centrifugation, disposing the centrate (119) followed by transferring the centrifuged solid mass with minimum 65% moisture content to alkali mixing tank (120);

[0031] 5. feeding alkali to the alkali mixing tank (120) from an alkali dosing system (121) connected to the alkali mixing tank (120) and mixing with the centrifuged solid mass to obtain a mixture, maintaining the pH of the mixture within a range of pH 9.5-10.5, preferably pH 10;

[0032] 6. transferring the mixture to a centrifuge 2 (123) with the help of a centrifuge feed pump 2 (122) and centrifuged to separate the sediment (128) and supernatant liquid phases;

[0033] 7. transferring the supernatant liquid to the alkali tank (125) for regeneration of the alkali, transferring the spent alkali (127) to the alkali mixing tank (120) by alkali recycle pump (126] for recycling; 8. transferring the sediment (128) from the centrifuge (123) to the hypoclorite treatment tank (129) and dosing NaOCl on the recovered biosolids in the tank (129);

[0034] 9. transferring the mixture to centrifuge 3 (131) by a centrifuge feed pu[mp (130), subjecting the mixture to centrifugation and transferring the centrate to the hypochloride regeneration tank (133), obtaining and transferring the recycled NaOCl solution to the hypocloride treatment tank (129) through a transfer pump (134);

[0035] 10. subjecting the centrifuged solid sediment containing the raw PHA (132) mixed with other proteins, to washing with acetone, to completely remove the protein remnants, leaving the pure PHA, subjecting the mixture to centrifugation (137) to obtain pure PHA as a concentrated solids mass (139).

[0036] In accordance with an alternative embodiment of this invention, in step 2, Ultra Filtration (UF) Membrane separation System is successfully used instead of sludge separation done in the sludge separator (109), and in step 3, the concentrate is separated and the permeate is transferred to the spent acid mixing tank (102). Poly aniline based acid resistant UF membrane suitable for MBR application gave best results.

[0037] In accordance with this invention is provided a process for extraction of Polyhydroxyalkanoates (PHA) from the host biomass, generated from agro-based wastewater treatment processes, in a continuous mode reactor train integrated within a continuous mode ETP operation process. The optimized extraction process has the following steps:

[0038] STEP 1

[0039] The PHA rich mixed culture waste activated sludge (WAS) is dewatered by basket centrifuge [Make Avdoot Centrifuge, 3000 rpm, rotor drum SS304 internal, 0.5 HP] to achieve minimum 65% moisture content prior to entering into the extraction process. This dewatered PHA rich sludge (101) first subjected to acid treatment in acid mixing tank (102) at 5% w / v ratio. Tank (102) is fitted with a mixer (103) [Make: REMI, Teflon coated shaft and impeller, 100 rpm, geared motor 0.5 HP] for proper mixing of the Sulphuric Acid (H2SO4) with water to maintain acid solution concentration of 3.5% (v / v) (0.64 M). The pH adjustment is continuously maintained through a pH controller [Make: E&H] and acid dosing system in the Acid Mixing Tank (102). STEP 2

[0040] The mixed acidic biomass is then transferred through sludge digestion feed pump

[0104] to the sludge digestion tank (105). The tank (105) is fixed with a mixer (106) and is placed inside an oil bath (107) for temperature control. The temperature is kept at a temperature in the range of 80°C to 90°C, preferably 80°C, to get the ideal conditions for lysing of the bacterial cells.

[0041] The sludge digestion tank (105) is made of borosilicate glass [Make: Borosil®] of total 18 litre capacity and round bottom for uniform heat distribution to the biomass mixed acidic solution. Active volume of the solution was 12 litres, maintaining the hydraulic retention time [HRT] in the acid digester for 6 hours, where the pump (104) is operated at 2 litres per hour [33.33 mL / min]. Feed pump (104) is peristaltic type [Make: Kamoer Model: FX STP 2 WiFi] with operation range of 1 - 120 millilitre per min [mL / min] with 24 hours operation capacity. Mixer (106) [Make: REMI, Teflon coated shaft and impeller, 40 rpm, geared motor 0.5 HP] is a slow speed agitator, which continuously stirs the solution to allow uniform concentration in the tank (105). Oil bath is fabricated by SB Scientific Works, Kolkata comprising of Stainless Steel [SS] internals and Mild Steel [IS 304] outer body with L&T make electrical switchgears. Oil is light liquid paraffin oil [boiling point 150°C].

[0042] Continuous pumping of biomass mixed acid solution to tank (105) allows overflow from the tank (105) of same quantity of liquid which is passed through spiral glass [Make: Borosil®] cooling jacket (108) and subjected to sedimentation by gravity settling in the sludge separator (109). The sludge separator is a closed type separating funnel made of borosilicate glass [Make Borosil®].

[0043] In accordance with an alternative embodiment of this invention, the sludge separation is done by ultrafiltration by (UF) membrane system instead of sludge separator (109).

[0044] STEP 3

[0045] In the sludge separator (109) tank the acid digested biomass gets settled while the supernatant acidic overflow (110) enters the transfer tank (112) [Volume 3 litre, top open, Make Borosil®]. This transfer tank is also fitted with a mixer ([111) [Make: REMI, Teflon coated shaft and impeller, 100 rpm, geared motor 0.5 HP] to uniformly mix the spent acid. This regenerated spent acid is transferred to acid mixing tank (102) preferably by a pump [not in figure] for further reuse. This process helps in minimizing the acid usage for sludge digestion. The pH is continuously maintained by the acid dosing system and the pH controller [Make E&H],

[0046] In accordance with the embodiment wherein the sludge is separated by ultrafiltration through an ultrafiltration membrane, the concentrate will be separated and the permeate will be transferred to the spent acid mixing tank (102).

[0047] STEP 4

[0048] The lysed biomass that is settled at the separation tank (109) bottom, is pumped (114) by solids transfer pump [Make: ROTO, Screw type, Rotor nitryl coated, 1 HP] to the neutralization tank (116). The tank (116) made of borosilicate glass [Make Borosil®] and has a mixer (115) [Make: REMI, Teflon coated shaft and impeller, 100 rpm, geared motor 0.5 HP] for uniform mixing and washing of the biomass with water, where continuous water addition is done for reducing the residual acid content. From tank (116), the mixture is taken to the centrifuge 1 (118) [Make Avdoot Centrifuge, 3000 rpm, rotor drum SS304 internal, 0.5 HP], using the centrifuge feed pump 1 (117). The centrate (119) is disposed to ETP. The centrifuged solid mass with minimum 65% moisture content is taken to alkali mixing tank (120).

[0049] This process consisting small quantity of liquid solutions is optimal to use the basket centrifuge system. However, for larger operations solid bowl centrifuge [Make: Penwaltt / Alfa Laval / Humbolt / Equivalent] is recommended.

[0050] STEP 5

[0051] The alkali mixing tank ([120) [Make: Reliable MS IS 2062 fabricated, Epoxy coated] is fitted with a mixer (140) [Make: REMI, Teflon coated shaft and impeller, 100 rpm, geared motor 0.5 HP] for effective mixing. The tank is connected to an alkali dosing system

[0121] generating NaOH solution of concentration 0.5 M and feeding to the alkali mixing tank

[0120] . The pH is controlled by pH controller [Make: E&H] to maintain the pH within a range of 9.5 to 10.5, preferably pH 10, to attain proper extraction conditions.

[0052] STEP 6

[0053] The mixture is next sent to the centrifuge 2

[0123] with the help of a centrifuge feed pump 2

[0122] and centrifuged to separate the phases. STEP 7

[0054] The supernatant liquid is taken to the alkali tank for regeneration

[0125] of the alkali. This tank is having a mixer

[0141] for uniform mixing of spent alkali

[0127] and transferred for recycling to the alkali mixing tank

[0120] by alkali recycle pump

[0126] . The pH adjustment is always maintained through the pH controller installed in the alkali mixing tank.

[0055] STEP 8

[0056] The sediment (128) from the centrifuge (123) [Make Avdoot Centrifuge, 3000 rpm, rotor drum SS304 internal, 0.5 HP] is taken to the hypocloride treatment tank [Make: Reliable MS IS 2062 fabricated, Epoxy coated] [(129) fitted with a mixer (142) [Make: REMI, Teflon coated shaft and impeller, 100 rpm, geared motor 0.5 HP]. In this tank (129], NaOCl of concentration 3 % (w / v) dosing is done by NaOCl Dosing System on the recovered biosolids. The residence time is kept 1 hour with room temperature in the Tank (129].

[0057] STEP 9

[0058] The mixture is transferred for centrifugation to the centrifuge 3

[0131] with the help of centrifugal feed pump

[0130] . The centrate is transferred to the hypochloride regeneration tank

[0133] which is fitted with a mixer

[0143] . The recycled NaOCl solution is taken to the hypocloride treatment tank

[0129] through a transfer pump

[0134] .

[0059] STEP 10

[0060] The centrifuged solid sediment contains the raw PHA

[0132] mixed with other proteins which is subjected to acetone wash where the protein remnants are dissolved in the acetone while the pure PHA remains unaffected. Total 3 step acetone wash is required in series for proper protein removal from the PHA. First acetone wash tank

[0135] is fitted with mixer

[0144] (Subsequent two step acetone wash tanks are similar in make and not shown in figure). The mixture is subjected to centrifugation

[0137] . The concentrated solids mass

[0139] is the extracted washed PHA. The supernatant spent acetone is collected in spent acetone tank and discarded

[0138] . Acetone wash is done under strict enclosed chamber with proper vent and acetone collection system maintaining air pollution control standard.

[0061] The projected production is 2.74 Kg / day (median) PHA based bioplastics considering extraction of PHA from 5.55 kg / day (median) dry organic biomass at 51.46% w / w recovery ratio utilizing the said process. The experimental results obtained from the continuous mode PHA extraction system is provided in Table- 1 below.

[0062] Table 1: Data obtained from continuous mode pha extraction system

Claims

CLAIMS:

1. An extraction process of Polyhydroxyalkanoates (PHA) from PHA-rich mixed culture waste activated sludge (WAS) in a Continuous Mode Reactor system comprising of a plurality of reactors and atleast a combination of reactors which are interconnected along the flow of the sludge biomass with digestion and extraction chemical systems, the process comprising the following steps:

1. subjecting PHA rich mixed culture waste activated sludge (WAS) to dewatering to obtain a dewatered PHA rich sludge (101) with minimum 65% moisture content, followed by acid treatment of the sludge in acid mixing tank (102);2. transferring the mixed acidic biomass through sludge digestion feed pump (104) to the sludge digestion tank (105), maintaining a temperature in the range of 80°C to 90°C for lysing of the bacterial cells, and continuously pumping of biomass mixed acid solution to tank (105) to allow overflow of liquid from the tank (105) , said liquid being cooled in a cooling jacket (108) and subjected to sedimentation by gravity settling in the sludge separator (109) or UF separation system ;3. allowing the acid digested biomass to settle in the sludge separator (109) or separated by UF system and the supernatant or permeate spent acidic overflow(110) to enter the transfer tank (112) and therefrom transferred to the acid mixing tank (102) for reuse;4. pumping the lysed biomass settled at the sludge separator tank (109) bottom or sludge concentrate from UF system, by the sludge transfer pump (114) to the neutralization tank (116). washing the biomass with water to reduce the residual acid content, transferring the mixture to the centrifuge (118) using the centrifuge feed pump (117), followed by centrifugation, disposing the centrate (119) followed by transferring the centrifuged solid mass with minimum 65% moisture content to alkali mixing tank (120);5. feeding alkali to the alkali mixing tank (120) from an alkali dosing system (121) connected to the alkali mixing tank (120) and mixing with the centrifuged solid mass to obtain a mixture, maintaining the pH of the mixture at a pH in the range of 9.5-10.5;6. transferring the mixture to a centrifuge 2 (123) with the help of a centrifuge feed pump 2 (122) and centrifuged to separate the sediment (128) and supernatant liquid phases;7. transferring the supernatant liquid to the alkali tank (125) for regeneration of the alkali, transferring the spent alkali (127) to the alkali mixing tank (120) by alkali recycle pump (126) for recycling;8. transferring the sediment [128] from the centrifuge [123] to the hypoclorite treatment tank [129] and dosing NaOCl on the recovered biosolids in the tank [129];9. transferring the mixture to centrifuge 3 [131] by a centrifuge feed pump [130], subjecting the mixture to centrifugation and transferring the centrate to the hypochloride regeneration tank [133], obtaining and transferring the recycled NaOCl solution to the hypocloride treatment tank [129] through a transfer pump [134];10. subjecting the centrifuged solid sediment containing the raw PHA [132] mixed with other proteins, to washing with acetone, to completely remove the protein remnants, leaving the pure PHA, subjecting the mixture to centrifugation [137] to obtain pure PHA as a concentrated solids mass [139].

2. An extraction process of Poly hydroxy alkanoates (PHA) from PHA-rich mixed culture waste activated sludge (WAS) in a Continuous Mode Reactor system comprising of a plurality of reactors and atleast a combination of reactors which are interconnected along the flow of the sludge biomass with digestion and extraction chemical systems, comprising the following steps:STEP 1:-the said PHA rich mixed culture waste activated sludge (WAS) is dewatered by basket centrifuge to achieve minimum 65% moisture content prior to entering into the extraction process, the dewatered PHA rich sludge (101) first subjected to acid treatment in acid mixing tank 102 at 5% w / v solid concentration for proper mixing with the Sulphuric Acid (H2SO4) solution of concentration 3.5% (v / v) (0.64 M). The pH adjustment is continuously maintained through a pH controller and acid dosing system in the Acid Mixing Tank (102);STEP 2:-the said mixed acidic biomass is then transferred through sludge digestion feed pump (104) to the sludge digestion tank (105) placed inside an oil bath (107) at a temperature in the range of 80oC to 90°C, preferably 80°C, to get the ideal conditions for lysing of the bacterial cells, the active volume of the solution was 12 litres, maintaining the hydraulic retention time HRT in the acid digester for 6 hours, where the pump (104) is operated at 2 litres per hour [33.33 mL / min], a continuous pumping of biomass mixed acid solution to tank (105) allows overflow from the tank (105) of same quantity of liquid which is passed through spiral glass cooling jacket (108) and subjected to sedimentation by gravity settling in the sludge separator (109);STEP 3-in the sludge separator tank (109) or in UF separation system] the acid digested biomass gets settled or alternatively separated while the supernatant or alternatively permeate acidic overflow (110) enters the transfer tank (112) with a mixer (111) to uniformly mix the spent acid and this regenerated spent acid is transferred to acid mixing tank (102) for further reuse;STEP 4-the lysed biomass that is settled at the separation tank (109) bottom or alternatively concentrate, is pumped (114) by solids transfer pump to the neutralization tank (116) where the biomass is washed with continuous water addition for reducing the residual acid content, the mixture is subjected to centrifugation in the centrifuge (118) fed with feed pump (117) from the tank (116), the centrate (119) is disposed to waste treatment facility and the centrifuged solid mass with minimum 65% moisture content is taken to alkali mixing tank (120);STEP 5-the alkali mixing tank (120) is connected to an alkali dosing system (121) where NaOH solution of concentration 0.5 M is generated and fed to the alkali mixing tank 120 at a pH in the range 9.5 to 10.5, preferably 10 to attain proper extraction conditions;STEP 6-the mixture is then sent to the centrifuge (123) with the help of a centrifuge feed pump 2 (122) and centrifuged to separate the phases;STEP 7-the supernatant liquid is taken to the alkali tank (125) for regeneration of the alkali, the spent alkali (127) is transferred for recycling to the alkali mixing tank (120) by alkali recycle pump (126);STEP 8-the sediment (128) from the centrifuge (123) is taken to the hypocloride treatment tank (129) fitted with a mixer (142), NaOCl of concentration 3 % (w / v) dosing in this tank (129) is done by NaOCl Dosing System on the recovered biosolids and the residence time is kept 1 hour with room temperature in the tank (129);STEP 9-the mixture is then transferred for centrifugation to the centrifuge (131) with the help of centrifugal feed pump (130), the said centrate is transferred to the hypochloride regeneration tank (133) and the recycled NaOCl solution is taken to the hypocloride treatment tank (129) through a transfer pump (134);STEP 10-the centrifuged solid sediment contains the raw PHA (132) mixed with other proteins which is subjected to acetone wash where the protein remnants are dissolved in the acetone while the pure PHA remains unaffected.

3. The extraction process of Polyhydroxyalkanoates (PHA) as claimed in the preceding claims, wherein in step 2, the liquid being cooled in a cooling jacket (108) is subjected to ultra-filtration, instead of sludge separation in a sludge separator (109) by a Poly aniline acid resistant MBR ultrafiltration membrane.

4. The extraction process of Polyhydroxyalkanoates (PHA) as claimed in claim 3, wherein in step 3, after the step of ultrafiltration, the concentrate sludge is subjected to downstreamsludge processing as mentioned in step 4 and the permeate is transferred to the spent acid mixing tank( 102).

5. The extraction process of Poly hydroxy alkanoates (PHA) as claimed in the preceding claims, wherein the pH adjustment is continuously maintained through a pH controller.

6. The extraction process of Polyhydroxyalkanoates (PHA) as claimed in the preceding claims, wherein the oil of the said oil bath (107) is light liquid paraffin oil.

7. The extraction process of Poly hydroxy alkanoates (PHA) as claimed in the preceding claims, wherein the said acetone wash is done under strict enclosed chamber with proper vent and acetone collection system maintaining air pollution control standard.

8. The extraction process of Poly hydroxy alkanoates (PHA) as claimed in the preceding claims, wherein the mixture is subjected to centrifugation (137) and the supernatant spent acetone is collected in spent acetone tank 138 and discarded.

9. A system for carrying out the extraction process of Polyhydroxyalkanoates (PHA) as claimed in the preceding claims, characterised by a tank (102) fitted with an acid mixer (103) and a pH controller, a sludge digestion feed pump (P4) (104), a sludge digestion tank (105) fixed with a mixer (106) and placed inside an oil bath (107) for temperature control, a sludge separator tank (109), OR Ultra Filtration Membrane separation System a transfer tank (112) fitted with a mixer (111), a sludge transfer pump (114), a neutralization tank (116) fitted with a mixer (115) and a centrifuge (118) with centrifuge feed pump (117), an alkali mixing tank (120) and a pH controller an alkali dosing system (121), a hypochlorite treatment tank (129) fitted with mixer (142) for treating PHA rich solids (128), and a centrifuge (131) with centrifuge feed pump (130),a hypochlorite tank (133) fitted with mixer (143) for regeneration of raw PHA (132) a transfer pump (134), an acetone wash tank (135) fitted with mixer (144) and a centrifuge (137) with centrifuge feed pump (136), an acetone tank (138), a control box (145), an electrical speed controller (146) and a reflux condenser (147).

10. The extraction process of Polyhydroxyalkanoates (PHA) as claimed in claim 1, wherein the production is 6.50 Kg / day PHA based bioplastics considering 50.95% w / w of biomass.

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