Biosynthesis of PHBs by the Method of Full-Factorial Design for Obtaining PHB/Magnetite Composites

Abstract

Various variants of poly(3-hydroxybutyrate) (PHB) were synthesized by varying three factors (sucrose concentration, phosphate concentration, and aeration level) while growing the producer Azotobacter vinelandii 12 using full-factorial design. Bacteria grown at elevated sucrose concentration, low phosphate concentration, and high aeration level (C+/P−/O+) showed the maximum PHB yield (0.49 g/L). Molecular weights (MW) of PHB samples obtained under diverse conditions differed by more than 30 times (from 49 to 1698 kDa). Low molecular weight PHBs were observed at low sucrose levels and high aeration (C–/O+). All other PHB samples had MW over 1200 kDa. The crystallinity of all PHB samples was determined by differential scanning calorimetry and was within the range of 62–68%. These results show that, with optimization, it will be possible to synthesize PHBs with different physicochemical properties for a wide range of biomedical problems, including tissue engineering.