Role of cultural variables in tailoring poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolymer synthesis in the diazotrophic cyanobacterium Aulosira fertilissima CCC 444

摘要

An important objective in the field of biopolymer research is to study the broad range of cultural conditions; by suitable choice of composition and processing conditions, polymer can often be tailor-made to have specific and desirable properties. Aulosira fertilissima CCC 444 when cultivated in a mixture of fructose and valerate produced poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] copolymer up to 537.5 mg L−1 containing 25 mol% 3HV monomers. Manipulation of the culture conditions such as varying pH, temperature, initial cell concentrations and dark incubation significantly affected the accumulation as well as composition of P(3HB-co-3HV) copolymer; therefore, the polymer finds a wider application. The molar fraction of 3HV tended to increase up to 35 mol% in the early phase of A. fertlissima cultivation, i.e. on the 7th day. An initial inoculum size of 80 mg dcw L−1 was found optimum for P(3HB-co-3HV) copolymer accumulation. Lower temperature conditions favoured the accumulation of copolymers containing higher molar fractions of 3HV monomers as compared to high temperature conditions. It was also observed that 3HV molar fractions in the copolymer can tailor up to 50 mol% by maintaining the pH of culture medium at 9.5, without significantly affecting the copolymer content (72 % dry cell weight). This opens up new possibilities of using A. fertilissima CCC 444 as a suitable feedstock for production of P(3HB-co-3HV) copolymer with varied 3HB and 3HV fractions for various industrial and pharmaceutical applications.