Abstract:
To study the factors that affected P(3HB) production by Bacillus megaterium BA-019 in order to increase the production yield of P(3HB) using sugarcane liquor which is inexpensive and locally available. The effects of initial concentration of sugarcane liquor and certain nutrients limitation (unbalanced growth condition) on cell growth as well as P(3HB) biosynthesis and accumulation were investigated. Limited amount of some components in the fermentation medium including nitrogen (urea), magnesium (MgSO4·7H2O) and a cooperation effect of potassium and phosphate (KH2PO4) was investigated. The results showed that B. megaterium BA-019 could grow and produce relatively high P(3HB) simultaneously when sugarcane liquor and urea were used as the carbon and nitrogen sources, respectively. An optimal fermentation medium yielding high P(3HB) production from B. megaterium BA-019 consisted of 30 g/l of total sugar in sugarcane liquor as a carbon substrate, 0.8 g/l of urea as a nitrogen substrate and 2.0 g/l of KH2PO4 with no requirement of MgSO4·7H2O addition. Under this condition, the maximum cell density of 9.21 g/l and P(3HB) concentration of 4.62 g/l (50.12% by DCW) were achieved at 12 h of cultivation. At the same time, the highest productivity of 0.38 g/l-h was also reached. Moreover, fermentation in 5 L fermenter was carried out using the same fermentation medium containing sugarcane liquor. The maximum cell density of 9.61 g/l and P(3HB) concentration of 3.07 g/l (42.52% by DCW) were reached at 6 h of cultivation as well as the highest productivity of 0.51 g/l-h. This results implied that the content of P(3HB) production in 5 L fermenter was lower than in shaken flask but cell density and P(3HB) productivity were higher than that of shaken flask cultivation.