Development of a Cost Effective Bioprocess for Prod uction of an Iranian Anti-Coleoptera Bacillus thuringiensis Strain

Abstract

One of the major obstacles of Bt production as a bi opesticide is its expensive bioprocess and fermentation. Therefore, the objective of the p resent study was to optimize growth condition and develop a low-cost bioprocess for mas s production of a native coleopteran- effective Bacillus thuringiensis (Bt) strain (KH4) based on agricultural wastes, at incubator and batch fermenter level. Preliminary ex periments showed that the optimum pH and temperature for the strain were 6.5 and 30°C, respectively. The maximum growth and spore/crystal production were observed in the m edium containing 2% molasses and 3% corn steep liquor as carbon and nitrogen sources, respectively. Different concentrations of the sea salt were used as a new c heap and available mineral source. Sea salt with final 0.003% w/w concentration showed the highest rate of growt h for the strain. The experiments in Batch fermenter showed that volu me of 2% bacterial inoculation in total volume of medium culture was the best concent ration as preculture. It was shown that pH significantly decreased at the beginning of logarithmic phase, whereas it significantly increased at the end of the logarithm ic phase. By increasing fermentation period, the oxygen demand was increased, and by inc reasing oxygen concentration up to 70% , the bacterial growth and the spores/crystal produ ction was increased. Based on the results, the growth condition of the strain was opt imized and a new cheap and available commercial fermentation medium was developed for ma ss production of the strain in the batch systems. Keywords : Agricultural waste, Bt, Economical growth media, Fermentation.