Effects of temperature, inoculum size and starch hydrolyzate concentration on butanediol production by Bacillus licheniformis.

An optimization study has been performed on 2,3-butanediol production by Bacillus licheniformis NCIMB 8059 from different carbon sources (glucose, sucrose and cornstarch hydrolyzate), alternately varying temperature (34<T<40 degrees C), inoculum size (0.5<X(0)<10 gl(-1)), and starting substrate concentration (20<S(0)<70 gl(-1)). The results of average volumetric productivity obtained from tests at variable temperature have been worked out according to Arrhenius to estimate the thermodynamic parameters of both 2,3-butanediol formation (Deltah(*)=69.5 kJ mol(-1); Deltas(*)=-0.12 kJ mol(-1)K(-1)) and thermal inactivation equilibrium (Deltah( composite function )(D)=179 kJ mol(-1); Deltas( composite function )(D)=0.73 kJ mol(-1)K(-1)). The highest butanediol yield on starting glucose (Y=0.87 mol x mol(-1)) and average diol plus acetoin productivity (nu(av)=0.58 gl(-1)h(-1)) were obtained on cornstarch hydrolyzate at T=37 degrees C, pH 6.0, X(0)=10 gl(-1); S(0)=30 gl(-1) which suggests some stimulation in this raw material of the fermentative metabolism of B. licheniformis. Therefore, cornstarch hydrolyzate can be proposed as an alternative carbon source for industrial production of 2,3-butanediol with no need for growth factor addition.