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.
