Molecular, Physiological and Biochemical Identification of Polyhydroxybutyrate Producing Streptomyces Isolated from Egyptian Localities

Abstract

T HE AMOUNT of chemosynthetic plastic waste increases every year and the exact time for its degradation is unknown. Polyhydroxybutyrates (PHBs) are macromolecules synthesized by bacteria. Because of their fast degradability under natural environmental conditions, PHBs were selected as alternatives for the production of biodegradable plastics. In the present study, soil samples were collected from the rhizosphere region of seven different crops commonly grown in Egyptian soils and used to collect Streptomyces isolates from Benha, Al-Qalioubia Governorate. A total of 50 representative actinomycete isolates (6 from lettuce, 5 from garlic, 9 from onion, 6 from zucchini, 9 from eggplant, 8 from wheat, 7 from alfalfa rhizosphere soil) were collected and refined. Screening was performed by staining colonies of isolates with Sudan Black B. The dye Sudan Black was used as a screening tool for PHB production. Streptomyces isolates were identified by morphological, biochemical and molecular methods. A phylogenetic tree constructed based on the resulting 16S rRNA-encoding gene sequences was examined. A Streptomyces isolate turned out to be Streptomyces incanus BK128. PHBpurified extract of Streptomyces incanus BK128 was characterized using FTIR in comparison to standard PHB. The authors investigated the effect of gamma irradiation on the activity of Streptomyces incanus BK128 on PHB production.