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 NCIMB8059 from different carbon sources (glucose, sucrose and cornstarch hydrolyzate), alternately varying temperature (34 < T < 40 C), inoculum size (0:5 < X0 < 10 g l 1), and starting substrate concentration (20 < S0 < 70 g l 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 (Dh ¼ 69:5 kJ mol 1; Ds ¼ 0:12 kJ mol 1 K 1) and thermal inactivation equilibrium (Dh D ¼ 179 kJ mol 1; Ds D ¼ 0:73 kJ mol 1 K 1). The highest butanediol yield on starting glucose (Y ¼ 0:87 mol mol 1) and average diol plus acetoin productivity (mav ¼ 0:58 g l 1 h 1) were obtained on cornstarch hydrolyzate at T ¼ 37 C, pH 6.0, X0 ¼ 10 g l 1; S0 ¼ 30 g l 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.