Scale Up Studies for Polyhydroxyalkanoate Production by a Bacillus flexus Strain with Industrial Potential

Abstract

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-hydroxybutyrateco-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.

PHBV cycle of life using waste as a starting point: from production to recyclability

“…Godoy and coworkers boosted this species of PHBV producer by performing an aerobic-anaerobic transition (Godoy et al, 2023). Other species such as B. cereus FA11 and Bacillus flexus can produce PHBV from glucose (Masood et al, 2012;Wagle et al, 2019). B. cereus can also produce PHBV using wheat starch wastewater (Sinaei et al, 2021).…”

“…They can be performed with different boundaries, which outcome in dissimilar calculations (Pawelzik et al, 2013). International LCA standards, like ISO 14040 and EB 16760, help guide the structure, conduct, limitations and assumptions for the general LCAs, although they are heterogeneous because of the different approaches and assumptions (Yates and Barlow, 2013;Spierling et al, 2018;Walker and Rothman, 2020).…”

Improving biological production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) co-polymer: a critical review

“…Various microorganisms have been studied using the main substrate without any precursors addition. Different species of Bacillus such as Bacillus circulans, Bacillus cereus, Bacillus Flexus and Bacillus OU40T produced PHBV when fed with sugars or industrial wastes (Masood et al 2012;Phukon et al 2012;Nagamani and Mahmood 2013;Wagle et al 2019). Pseudomonas aeruginosa, Yangia ND199 and Halomonas campisalis showed the same interesting capacity (Kulkarni et al 2010;Van-Thuoc et al 2015;Ali and Jamil 2017).…”

“…Optimum air flow was found to be 5.1 ml/min. Also, Wagle et al (2019) lowered the agitation and air inflow rate (rpm from 700 to 350 and vvm from 1 to 0.5) and increased the temperature from 28 to 37°C to favor PHBV production. The strategy resulted in an appreciable 36% increase in PHBV production and better substrate utilization.…”