BIOSYNTHESIS OF POLY(3-HYDROXYBUTYRATE-CO-3-HYDROXYVALERATE) BY A MUTANT OF SPHAEROTILUS NATANS

The copolyester of 3-hydroxybutyrate and 3-hydroxyvalerate was synthes ized from the combined carbon sources of glucose and sodium propionate by a filamentaion-defective mutant of Sphaerorilus natans, which is a typical filamentous bacterium often found in activated sludge. The 3- hydroxyvalerate content in the produced polymer increased with increas ing, concentrations of propionate. Cell growth and polyester synthesis were observed even when 0.6% sodium propionate was added to the mediu m: when the 3-hydroxyvalerate content in the polymer produced was abou t 60 mol%. The monomer composition of the copolymer was also varied by aeration conditions, time of propionate feeding, and cultivation time . This strain flocculated in accordance with cell growth, allowing rap id and convenient separation of the biomass from the culture fluid.