Polyhydroxyalkanoates (PHA) are synthesized by bacteria under unfavourable growth conditions like excess of carbon over nitrogen, coupled with oxygen limitation. The PHA polymers of microbial origin are diverse in chemical composition and material properties. A bioprocess for PHA production by indigenously isolated Bacillus flexus MTCC 12841 was devised and optimized at a laboratory fermentor scale. Fermentation strategies that involved modifications in some parameters like aeration, agitation, temperature, nutrient feeding or changes in C:N ratio led to substantial improvement of 59% in PHA production reaching highest concentration of 9.73 g/L. Biomass too was enhanced to 15.70 g/L equivalent to 126% increase over the optimized shake flask runs. PHA (Yp/s) and biomass (Yx/s) yields were found to be 0.32 and 0.51 g/g respectively, indicating good carbon utilization efficiency. The characterization of polymer by GC–MS revealed that the culture produced poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) as a co-polymer. The novelty of the research findings lies in the demonstration of increased production of PHA at lab fermentor level coupled with the identification of the natural ability of the strain to also produce PHBV without any need for exogenous addition of precursors. The fermentation process as well as the strain may be subjected to further optimization to increase the PHA production as well as to increase the % of HV content in the co-polymer.

中文翻译：

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由具有工业潜力的弯曲芽孢杆菌菌株生产聚羟基链烷酸酯的规模研究。

细菌在不利的生长条件下合成了多羟基链烷酸酯（PHA），例如碳比氮过量，以及氧气限制。微生物来源的PHA聚合物的化学组成和材料特性各不相同。本地分离的弯曲芽孢杆菌生产PHA的生物过程MTCC 12841是在实验室发酵罐规模上设计和优化的。发酵策略涉及一些参数的修改，例如通气，搅拌，温度，养分进料或C：N比的变化，导致PHA产量显着提高59％，达到最高浓度9.73 g / L。生物质也提高到15.70 g / L，相当于比优化的摇瓶运行增加了126％。发现PHA（Yp / s）和生物质（Yx / s）的产率分别为0.32和0.51 g / g，表明良好的碳利用效率。用GC-MS表征聚合物表明，培养物产生了聚3-羟基丁酸酯-co-3-羟基戊酸酯（PHBV）的共聚物。该研究发现的新颖之处在于证明了实验室发酵罐水平上PHA产量的增加，同时还证实了该菌株自然生产PHBV的天然能力，而无需任何外源添加前体。可以对发酵过程以及菌株进行进一步的优化，以增加PHA的产量以及增加共聚物中HV含量的百分比。