Method for production polyhydroxybutyric acid resin

A method for producing a polyhydroxybutyrate-based resin, comprising:

• disrupting or solubilizing microbial cells comprising a polyhydroxybutyrate-based resin;
• separating the polyhydroxybutyrate-based resin from the composition,
• drying the separated polyhydroxybutyrate-based resin, thereby producing the polyhydroxybutyrate-based resin, and discharging liquid waste as wastewater from the production of polyhydroxybutyrate-based resin,
• subjecting the wastewater discharged from the production of polyhydroxybutyrate-based resin to microbial anaerobic and aerobic treatment,
• pre-filtering the wastewater obtained from the microbial anaerobic and aerobic treating using a membrane bioreactor process,
• filtrating the pre-filtered wastewater with a calcium ion removal membrane, thereby obtaining water, and
• reusing the obtained water in the production of the polyhydroxybutyrate-based resin,
• wherein the water has a calcium ion concentration of 4.5 mg/L or less,
• wherein the calcium ion removal membrane is at least one selected from the group consisting of a nanofiltration (NF) membrane and a reverse osmosis (RO) membrane, and
• wherein an MgSO4 rejection rate of the NF membrane or the RO membrane at a temperature of 20° C. and under a pressure of 3000 kPa is from 60% to 100%.