Biodegradation of poly-beta-hydroxybutyrate by microscopic fungi

Among 34 strains of microscopic fungi belonging to the genera Penicillium, Absidia, Gilbertella, Mucor, and Rhizopus, 20 were able to utilize poly-bet a-hydroxybutyrate (PHB). Aspergillus caespitosus VKM F3643 and variant AB-1 of Penicillium funiculosum KBP MGU 146 were the most potent PHB degraders. Investigation of growth characteristics and consumption of PHB by fungi gr own in mineral medium showed that the bottleneck of PHB utilization was the decrease in the pH of the growth medium to values lower than 3.0. The main tenance of pH in a physilogical range of 3.5-7.0 led to complete degradatio n of PHB in less than two weeks. The polymer was utilized with the involvem ent of extracellular depolymerases, Analysis by the method of mass;energy b alance showed that the growth characteristics of fungi grown on PHB (Y-X/S = 0.5 and eta = 0.35) and the degree of polymer reduction (gamma(S) = 4.76) are close to the respective parameters in the case of utilization of n-alk anes.