Comparative Study of Methods of Pha Extraction from Bacterial Biomass

A comparative study of different methods of PHA extraction from the biomass of bacteria was carried out. It was shown that different reagents and process technologies have different effects on the extraction results - the completeness of polymer extraction and degree of its purity. Application of chloroform requires the use of large amounts of volatile and toxic reagents. When dichloromethane is used, the completeness of extraction increases, but it becomes necessary to implement procedures for separating the "extractant-precipitator" mixture. The solvent-precipitator pair (dichloromethanehexane) was selected, which does not lead to formation of an azeotropic mixture, making it possible to return up to 90% of the reactants to the process. As a result, solvent consumption went down from 73.5 kg/kg of PHA (chloroform - hexane) to 63.7 kg/kg of PHA (chloroform - ethanol - hexane). If ethanol is excluded, it is possible to reduce the consumption to 7.8 g/g of PHA, but in this case additional treatment of biomass to destroy membrane complexes or sequential treatment first with alcohol and then with dichloromethane is needed. A nonchemical method using sodium dodecyl sulfate (NaDS) as a detergent allows for a more economical way to obtain high yields of polymer not contaminated with admixtures of fatty acids and suitable for technical purposes (packaging, packaging products). A combined method was developed, which considerably reduces the cost of reagents and makes it possible to obtain polymers with high purity degree and extraction completeness up to 98.5-99.0%.