Kefir yeast technology: scale-up in SCP production using milk whey.

A three-step process to scale-up kefir biomass production at a semi-industrial scale employing whey is reported. Aerobic fermentations were initially performed at laboratory scales, in 1.5- and 4-L bioreactors, yielding 79 g/L final kefir biomass (0.89 g/g of lactose utilized), in 7 h of fermentation time. The use of whey as carbon source even in solid cultures led to the formation of a granular biomass. These results encouraged scale-up at a semi-industrial-scale pilot plant employing 100- and 3,000-L bioreactors, leading to the development of a process for granular kefir biomass production. The results validated the laboratory-scale experiments and the avoidance of centrifugal separators due to granular biomass formation. Pilot-plant operations showed kefir to be highly resistant to contamination under actual industrial conditions and no serious problems in handling of raw materials and equipment were observed. Economic analysis showed a 20% higher cost of the market price of products, with added value of up to 15.9 x 10(9) within the European Union.

Grape and apple wines volatile fermentation products and possible relation to spoilage.

The main volatile by-products of the alcoholic fermentation of grape wine, cider and apple pulp wine were investigated to determine if any correlated with spoilage resistance in the latter two. Spoilage was visually detected after seven days in low-alcohol grape wine in comparison to 11 and 16 days in cider and apple pulp wine, respectively. Acetaldehyde, ethyl acetate, methanol, propanol, isobutanol and amyl alcohols were the main fermentation by-products detected in all three wines. There were highest concentrations of acetaldehyde, ethyl acetate, methanol and propanol in grape wine and, therefore, these by-products could not be implicated in spoilage resistance in apple wines. Increased concentrations of isobutanol and amyl alcohols, however, in cider and apple pulp wine in comparison to grape wine might have been the reason for spoilage resistance in the apple wines.

Delignified cellulosic material supported biocatalyst as freeze-dried product in alcoholic fermentation.

Freeze-dried delignified cellulosic (DC) material supported biocatalyst is proposed as a suitable form of biocatalyst to be preserved. The alcoholic fermentation of glucose using freeze-dried immobilized cells is reported. Freeze-dried immobilized baker's yeast cells on DC material do not need any protective medium during freeze-drying. The effect of initial glucose concentration and temperature on the alcoholic fermentation kinetic parameters is reported in the present study. It was found that the freeze-dried immobilized cells ferment more quickly than free freeze-dried cells and have a lower fermentation rate as compared with wet immobilized cells. However, repeated batch fermentations showed freeze-dried immobilized cells to ferment at about the same fermentation rate as wet immobilized cells. The results indicate that the freeze-dried immobilized cells must be further studied to establish a process for the preservation of immobilized cells.