The effects of mixing, temperature, and nutrient concentration on the fermentation of a mixed sugar solution simulating the hexose content of waste sulfite liquor

The results of changes in temperature, mixing and nutrient concentration on the conversion by yeast of D‐mannose, D‐galactose, and D‐glucose using Saccharomyces cerevisiae strain were studied. These sugars are present in waste sulfite liquor. From the operating conditions used in this study, the most rapid removal of sugars found at a pH of 5 were temperature 36°C, mixing 700 rpm, and nutrient concentration 13.3 g/1. The fermentation was carried in a three‐litre batch reactor and the main variables measured were dissolved oxygen, yeast growth, alcohol production, total sugar consumption, and D‐mannose, D‐galactose and D‐glucose utilization. It was found that the fermentation could be fitted to the published Kono‐Assai model.