Abstract
There has been considerable interest in development and industrial production of polyhydroxybutyrate (PHB) biopolymers from bacteria due to its potential applications in agriculture, health and medicine. However, it is recommended to evaluate PHB-producing bacteria regarding sensitivity to antibiotics, resistance to heavy metals and possible toxicity before large scale production of the biopolymer. In this study, 120 bacterial strains isolated from different soil and sewage water samples in Eastern Province, Saudi Arabia, and screened for PHB production. Sixteen strains showed positive results with Sudan Black B and Nile Red A stains. 16S DNA gene analysis revealed high homologies to members of Bacillus cereus group, B. megaterium, B. flexus, B. endophyticus, and B. aryabhattai. For antibiotic profiling; B. cereus DS3-16 and B. thuringiensis DST1-33 showed highest resistance, especially to ampicillin, erythromycin and amoxicillin, while the least were B. megaterium DG8, DP7 and B. pseudomycoides DWST2-1. Bacillus sp. DSG5 and DPS6 followed by DSWT2-1, DS3-17 and DS3-12 showed highest resistance to Cr+6 (10 mg/mL), as well as Hg (62.5 mu g/mL) and Ag (5 mg/mL), respectively while most strains were highly susceptible to other metals. Four isolates including B. cereus strain DS3-16 showed beta-hemolysis activity, while Bacillus axarquiensis DSG5 showed a-hemolytic activity, indicating their possible toxicity. (C) 2016 Friends Science Publishers