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)), Na(2)HPO(4) 2H(2)O (2.2-6.2 g l(-1)), KH(2)PO(4) (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, Na(2)HPO(4) 2H(2)O-2.2, KH(2)PO(4) - 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.
In this paper, effect of different carbon and nitrogen sources, including hydrolysates of rice bran and wheat bran, on simultaneous production of α-amylase (for hydrolysis of starch in food systems) and polyhydroxyalkanoates
The antioxidative properties of ascorbyl palmitate (AP) alone and in combination with other known antioxidants were investigated during deep fat frying of potato chips in peanut oil. Their effect on the quality of the frying oil and shelf‐life of the fried product were studied. The other antioxidants tested were butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and propyl gallate (PG). The characteristics evaluated for the frying oil were color development, viscosity, peroxide value (PV) and polymerization of the oil during deep fat frying; AP was found to reduce these values. It also helped to prevent the degradation of the oil by retaining the unaltered triacylglycerols during the frying period. Addition of AP to the frying oil reduced the PV of the extracted fat, doubled the shelf‐life of the fried product and improved the quality of frying oil with increase in frying time. However, AP did not show any synergistic effect with other antioxidants examined.
Aims: The objective of the present work was to utilize an unrefined natural substrate namely mahua (Madhuca sp.) flowers, as a carbon source for the production of bacterial polyhydroxyalkanoate (PHA) copolymer by Bacillus sp‐256.
Methods and Results: In the present work, three bacterial strains were tested for PHA production on mahua flower extract (to impart 20 g l−1 sugar) amongst which, Bacillus sp‐256 produced higher concentration of PHA in its biomass (51%) compared with Rhizobium meliloti (31%) or Sphingomonas sp (22%). Biosynthesis of poly(hydroxybutyrate‐co‐hydroxyvalerate) – P(HB‐co‐HV) – of 90 : 10 mol% by Bacillus sp‐256 was observed by gas chromatographic analysis of the polymer. Major component of the flower is sugars (57% on dry weight basis) and additionally it also contains proteins, vitamins, organic acids and essential oils. The bacterium utilized malic acid present in the substrate as a co‐carbon source for the copolymer production. The flowers could be used in the form of aqueous extract or as whole flowers. PHA content of biomass (%) and yield (g l−1) in a 3·0‐l stirred tank fermentor after 30 h of fermentation under constant pH (7) and dissolved oxygen content (40%) were 54% and 2·7 g l−1, respectively. Corresponding yields for control fermentation with sucrose as carbon source were 52% and 2·5 g l−1. The polymer was characterized by proton NMR.
Conclusions: Utilization of mahua flowers, a natural substrate for bacterial fermentation aimed at PHA production, had additional advantage, as the sugars and organic acids present in the flowers were metabolized by Bacillus sp‐256 to synthesize P(HB‐co‐HV) copolymer.
Significance and Impact of the Study: Literature reports on utilization of suitable cheaper natural substrate for PHA copolymer production is scanty. Mahua flowers used in the present experiment is a cheaper carbon substrate compared with several commercial substrates and it is rich in main carbon as well as co‐carbon sources that can be utilized by bacteria for PHA copolymer production.
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