Degradation of poly(3-hydroxybutyrate) by soil streptomycetes

The ability of 64 soil streptomycetes to degrade poly(3-hydroxybutyrate) [P (3HB)] was evaluated on Pridham and Lyons mineral salts agar medium overlay ered with the same medium containing 0.2% P(3HB). The streptomycete isolate s were grown on this overlayered medium and the degradation was detected by the formation of clear zone surrounding the growth. Four potent degrader i solates identified as species of Streptomyces were selected. Degradation of P(3HB) by these isolates was studied for a period of 8 days. The rate of d egradation increased with increase in concentration of P(3HB) in the medium while it decreased with the supplementation of readily utili- zable carbon sources like glucose, fructose and sucrose. All four isolates also degrade d the copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate [P(3HB-co-3HV)] in solid medium but to a lesser extent. However, the isolates were equally efficient in degrading P(3HB) in liquid medium.