Abstract
Polyhydroxyalkanotes (PHAs), the eco-friendly biopolymers produced by many bacteria, are gaining importance in curtailing the environmental pollution by replacing the non-biodegradable plastics derived from petroleum. The present study was carried out to economize the polyhydroxybutyrate (PHB) production by optimizing the fermentation medium using corn steep liquor (CSL), a by-product of starch processing industry, as a cheap nitrogen source, by Bacillus sp. CFR 256. Response surface methodology (RSM) was used to optimize the fermentation medium using the variables such as corn steep liquor (5–25 g l−1), Na2HPO4 2H2O (2.2–6.2 g l−1), KH2PO4 (0.5–2.5 g l−1), sucrose (5–55 g l−1) and inoculum concentration (1–25 ml l−1). Central composite rotatable design (CCRD) experiments were carried out to study the complex interactions of the variables.
The optimum conditions for maximum PHB production were (g l−1): CSL-25, Na2HPO4 2H2O-2.2, KH2PO4 − 0.5, sucrose − 55 and inoculum − 10 (ml l−1). After 72 h of fermentation, the amount of PHA produced was 8.20 g l−1 (51.20% of dry cell biomass). It is the first report on optimization of fermentation medium using CSL as a nitrogen source, for PHB production by Bacillus sp.
Keywords: Bacillus, Corn steep liquor, Central composite rotatable design, Optimization, Polyhydroxybutyrate, Response surface methodology
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References
- 1.Lee Y.L. Bacterial polyhydroxyalkanoates. Biotechnol Bioeng. 1996;49:1–14. doi: 10.1002/(SICI)1097-0290(19960105)49:1<1::AID-BIT1>3.0.CO;2-P. [DOI] [PubMed] [Google Scholar]
- 2.Son H., Park G., Lee S.Growth-associated production of poly-β-hydroxybutyrate from glucose or alcoholic distillery wastewater by Actinobacillus sp. EL-9 Biotechnol Lett 1996181229–1234.10.1007/BF00129945 [Google Scholar]
- 3.Rusendi D., Sheppard J.D.Hydrolysis of potato processing waste for the production of poly-beta-hydroxybutyrate Bioresour Technol 199554191–196.10.1016/0960-8524(95)00124-7 [Google Scholar]
- 4.Page W.J.Production of poly-beta-hydroxybutyrate by Azotobacter vinelandii UWD in media containing sugars and complex nitrogen sources Appl Microbiol Biotechnol 199238117–121.10.1007/BF00169430 [Google Scholar]
- 5.Hunter J.S. Determination of optimum conditions by experimental methods. Ind Qual Control. 1996;15:6–16. [Google Scholar]
- 6.Triveni R., Shamala T.R., Rastogi N.K.Optimized production and utilization of exopolysaccharide from Agrobacterium radiobacter Process Biochem 200136787–795.10.1016/S0032-9592(00)00279-X [Google Scholar]
- 7.Kshama L., Rastogi N.K., Shamala T.R.Simultaneous and comparative assessment of parent and mutant strain of Rhizobium meliloti for nutrient limitation and enhanced polyhydroxyalkanoate (PHA) production using optimization studies Process Biochem 2004391977–1983.10.1016/j.procbio.2003.09.021 [Google Scholar]
- 8.Patnaik P.R. Perspectives in the modeling and optimization of PHB production by pure and mixed cultures. Crit Rev Biotechnol. 2005;25:153–171. doi: 10.1080/07388550500301438. [DOI] [PubMed] [Google Scholar]
- 9.Cochran W.G., Cox G.M. Experimental designs. 2nd edn. Bombay: Asia publishing House; 1977. [Google Scholar]
- 10.Saxena D.C., Rao P.H.Optimization of ingredients and process conditions for the preparation of tandoori roti using response surface methodology Int J Food Sci Technol 199631345–351.10.1046/j.1365-2621.1996.00339.x [Google Scholar]
- 11.Law J.H., Slepecky R.A. Assay of poly-beta-hydroxy butyric acid. J Bacteriol. 1961;82:33–36. doi: 10.1128/jb.82.1.33-36.1961. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 12.Williamson D.H., Wilkinson J.F. The isolation and estimation of poly-β-hydroxy-butyrate inclusions of Bacillus species. J Gen Microbiol. 1958;19:198–200. doi: 10.1099/00221287-19-1-198. [DOI] [PubMed] [Google Scholar]
- 13.Wilkinson J.F., Munro A.L.S. The influence of growth limiting conditions on the synthesis of possible carbon and energy storage polymers in Bacillus megaterium. In: Powell E.O., Evans C.G.T., Strange R.E., Tempest D.E., editors. Microbial physiology and continuous culture. London: H.M.S.O.; 1967. pp. 173–185. [Google Scholar]
- 14.Cho C.H., Jeong S.J., Kim J.W. Stimulation of poly (3-hydroxybutyrate) degradation by nitrogen nutrient in Alcaligenes eutrophus H16. Korean Biochem J. 1994;27:316–322. [Google Scholar]
- 15.Borah B., Thakur P.S., Nigam J.N. The influence of nutritional and environmental conditions on the accumulation of poly-beta-hydroxybutyrate in Bacillus mycoides RLJ B-017. J Appl Microbiol. 2002;92:776–783. doi: 10.1046/j.1365-2672.2002.01590.x. [DOI] [PubMed] [Google Scholar]
- 16.Fouchet P., Jan S., Courtois J., Courtois B., Frelat G., Barbotin J.N. Quantitative single cell detection of poly (β-hydroxybutyrate) accumulation in Rhizobium meliloti by flow cytometry. FEMS Microbiol Lett. 1995;126:31–36. [Google Scholar]
- 17.Tombolini R., Nuti M.P. Poly(β-hydroxyalkanoate0 biosynthesis and accumulation by different Rhizobium species. FEMS Microbiol Lett. 1989;60:299–304. [Google Scholar]