Dissolved oxygen as a propulsive parameter for polyhydroxyalkanoate production using Bacillus endophyticus cultures

Geethu Madhusoodanan,Divyashree Somashekara,Raghu Chandrashekar Hariharapura

doi:10.1007/s10668-021-01626-3

Geethu Madhusoodanan, Divyashree Somashekara + Show 1 more

Open Access

https://doi.org/10.1007/s10668-021-01626-3

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Abstract

Conventional biopolymers resembling synthetic polymers produced from microorganisms, polyhydroxyalkanoate (PHA) synthesized utilizing renewable resources have gained supreme attention recently. PHA accumulation within the microbial cell is an innate capability of bacteria to store carbon and energy when nutrient imbalance pertains. Gram positive Bacillus endophyticus capable of synthesizing PHA was focused in this study. Study focuses on the possibility of attaining high PHA yield in relation to the varying dissolved oxygen levels induced during production phase. There was a gradual increment in PHA production from 34.5 to 53.03% when cultivated in bioreactor that maintained least dissolved oxygen of 0.4 mg/L at 32 °C. The metabolic flux of organism was altered during oxygen stress brought by varying agitation rate and volume resulting in the accumulation of Nicotinamide Adenine Dinucleotide Hydrogen (NADH), which led to increase in the overall PHA production. PHA yield was found to be favored by decreasing the oxygen supply thereby inducing an oxygen stress environment. This report was the first one that was correlating the hypothesis that links PHA yield and oxygen stress condition during production phase. PHA produced was characterized by FTIR and 1HNMR spectra in which the presence of Polyhydroxybutyrate was confirmed.Graphical abstract

Highlights

Worldwide interest to use bio-based polymers has been accelerated as an eco-friendly alternative to plastic
Conventional biopolymers resembling synthetic polymers produced from microorganisms have gained supreme attention as they synthesize the building blocks utilizing the renewable resources
Biopolymer production was conducted in a statistically optimized production medium (PM), composition (g/L): N a2HPO4 2H2O 2.2, KH2PO4 1.5, (NH4)2SO4 1.5, MgSO47H2O 0.2, Sucrose 20–40 g/L: PM I: 20 g/L, PM II: 40 g/L. in cotton plugged 250 mL Erlenmeyer flask with three different volumes (50, 100 and 150 ml) and to study the role of agitation and aeration on PHA production, Bacillus endophyticus was cultivated in production medium with a fixed volume of 50 mL in a 250 mL

Summary

Introduction

Worldwide interest to use bio-based polymers has been accelerated as an eco-friendly alternative to plastic. Their physio-chemical properties can overcome the increased demands in the rapidly developing fields like biomedical and industrial sector (Ojumu et al, 2004). Conventional biopolymers resembling synthetic polymers produced from microorganisms have gained supreme attention as they synthesize the building blocks (monomer) utilizing the renewable resources. Among the microbial synthesized biopolymers, Polyhydroxyalkanoates (PHA) are gaining much attention due to their similar material properties toward plastic (Zheng et al, 2020; Chen and Jiang, 2018). PHA are polymers synthesized entirely by a biological process within the cytoplasm as inclusion bodies (Sathya et al, 2018) and are naturally occurring aliphatic polyesters produced by more than 75 genera of gram positive and gram negative bacteria.

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