Influence of heat shock on glycerol production in alcohol fermentation.

The influence of single and double heat shocks induced during the exponential growth phase of the Saccharomyces cerevisiae fermentation of cultivar Sauvignon Blanc grape must was examined. Rapid temperature changes from 18 degrees C to 34 degrees C have been applied. The effect of the duration of exposure to a high temperature has been analyzed. By the applications of a single heat shock and a double heat shock, up to 8.2 g l(-1) and 11.0 g l(-1) glycerol have been produced, respectively. To prevent the evaporation of fine wine bouquet compounds during the temperature changes, reflux coolers on the top of bioreactors have been employed. By using this method, glycerol production was increased by up to 65%.

Effect of Solid State Fermentation Medium Optimization on Pleurotus ostreatus Laccase Production.

The objective of this work was to increase laccase production by Pleurotus ostreatus PLAB through culture medium optimization using solid state culture conditions. Increased laccase activity was obtained through design of experiments (DOE) using the Taguchi orthogonal array (OA). Seven factors, viz. lignocellulose, glucose, yeast extract, peptone, KH(2)PO(4), MgSO(4) 7H(2)O and MnSO(4) H(2)O at three levels and pH at two levels. OA layout of L18 (2(1) x 3(7)) was selected for the proposed experimental design using Minitab 17 software. Data analysis showed that lignocellulose (20 %) and glucose (10 g L1) had positive effect, whereas KH(2)PO(4), MgSO(4)∙7H(2)O and MnSO(4)∙H(2)O did not have significant effect on laccase production. Taguchi OA analysis showed that pH 6, lignocellulose 20 %, glucose 10 g L(-1), yeast extract 6 g L(-1), peptone 15 g L(-1), KH(2)PO(4) 3 g L1, MgSO(4)∙7H(2)O 0.5 g L(-1) and MnSO(4)∙H(2)O 0.1 g L-1 were the optimal conditions to maximize laccase production. The model predicted a 30.37 U g(-1) dry wt., which agreed with the experimentally obtained laccase activity 29.15 U g(-1) dry wt. at optimal conditions.