Poly-3-hydroxybutyrate (PHB) is a biodegradable polymer produced by many bacteria. Some of the properties are similar to thermoplastics like polypropylene, hence finding application PHB can directly replace non-biodegradable polymers. But the main barrier has been the cost difference. The utilization of mixed microbial cultures facilitates the use of complex substrates and thus can reduce the cost of PHB production. In the present study, mixed culture systems, where metabolite produced by one organism may be assimilated by the other organism, were employed. Bacillus firmus NII 0830, the first organism, was used for the production of PHB since it accumulates a large amount of PHB, while the second organism, Lactobacillus delbrueckii NII 0925, was used to provide acetic acid. Enzyme kinetic studies were performed on the PHB biosynthetic enzymes, such as β-ketothiolase, acetoacetyl CoA reductase and PHB synthase. PHB production by mixed culture was higher when compared to pure cultures. The mathematical model was then fitted to the experimental data, which can describe the dynamics of a mixed culture. The β-ketothiolase and acetoacetyl CoA reductase showed a Vmax value of 0.0093 μM/min and 0.0253 μM/min, respectively. The Km values were 140.8 μM and 183.5 μM, respectively. The enzyme kinetic studies gave an idea about the action of the enzymes.
Authors are grateful to the Department of Biotechnology, Government of India, New Delhi, for financial support of the project. One of the authors, Raveendran Sindhu, acknowledges the Department of Biotechnology for financial support under DBT Bio-CARe scheme. Raveendran Sindhu and Parameswaran Binod acknowledge European Commission Seventh Framework Programme, Marie Curie Actions-International Research Staff Exchange Scheme - Contact Number 318931.
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mixed culture biotechnology
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