PRODUCTION AND RECOVERY OF POLY-Β-HYDROXYBUTYRATEFROM WHEY DEGRADATION BY AZOTOBACTER
2007
Khanafari, A. | Sepahei, A. Akhavan | Mogharab, M.
Three strains of Azotobacter chroococcum were studied to produce poly-β hydroxybutyrate as a inclusion body by whey degradation. Optimum degradation whey results were obtained when using whey broth as a fermentation medium without extra salt, temperature at 35 °C and pH 7 (P<0.05). Lambda max for whey broth medium was determined probably about 400 nm. The effect of different nitrogenous rich compounds (NH4NO3, Bactopeptone, Casein, Yeast extract, Meat extract, Protease peptone and Tryptone) on whey degradation showed that incorporation of nitrogenous compounds into the medium did not increase whey degradation by Azotobacter chroococcum 1723 (P<0.05). But poly-βhydroxyl-butyrate production was increased in presence Meat extract up to 75% of the cell dry weight after 48h. The addition of nitrogenous sourced (except ammonium nitrate) had a positive effect on poly-β hydroxyl-butyrate production as it peaked in the presence of Meat extract and 4.43 g/L was accumulated in comparison to 0.5g at diazotrophically growing cells. Increasing the O2 values resulted by shaking at 122 rpm in decreased poly-β hydroxyl-butyrate yield form 4.43 to 0.04 g/L. The results show that this medium supports the growth of strain 1735 and also that this waste could be utilized as a carbon and nitrogen source. Production of poly-β hydroxyl-butyrate by using whey as a medium looks promising, since the use of inexpensive feed-stocks for poly-β hydroxyl-butyrate is essential if bioplastics are to become competitive products.
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