Poly-β-hydroxy butyrate depolymerase from Streptomyces lydicus MM10, isolated from wastewater sample

Abstract

Plastics are an integral part in our daily life activities and it is difficult to conceive how we could function without them. Burning or chemical treatments of these plastic materials destroys the environment and have many dangerous effects on, water air and human health. Thus, other sources of plastic (biodegradable plastic) must be introduced. Under unfavorable growth conditions Poly ß-hydroxybutyrate (PHB) is accumulated intracellular by many bacteria and the principal enzyme for the degradation of PHB is PHB depolymerase. A number of thermophilic actinomycetes have been screened for PHB degradation on agar plats. All these isolates were recovered from soil, sand and wastewater samples on starch nitrate agar at incubation temperature of 45. Five isolates (50%) out of 10 showed degradation activities, detected by the diameter of the clear zone. The Actinomycete isolate MM10 was the most PHB degrader and it was identified using morphological, physiological and biochemical characters. According to 16SrRNA analysis, it was identified as Streptomyces lydicusMM10. Growth at 45°C, in minimal medium (pH7.0) containing glucose and0.3% PHB as enzyme inducer, enhanced enzyme production and maximum activity was obtained after 24 h of incubation. The PHB depolymerase was precipitated and purified using column chromatography. The optimum temperature and pH of the pure enzyme were 45°C and pH 8, respectively. However, production of bioplastics is cost effective as compared to synthetic plastics they were non-toxic and completely biodegradable by some actinomycete isolates.