Oxygen transfer in a stirred loop fermentor with dilute polymer solutions

The Production of Bioethanol from Cashew Apple Juice by Batch Fermentation Using Saccharomyces cerevisiae Y2084 and Vin13

Bioethanol as a fossil fuel additive to decrease environmental pollution and reduce the stress of the decline in crude oil availability is becoming increasingly popular. This study aimed to evaluate the concentration of bioethanol obtainable from fermenting cashew apple juice by the microorganism Saccharomyces cerevisiae Y2084 and Vin13. The fermentation conditions were as follows: initial sugar = 100 g/L, pH = 4.50, agitation = 150 rpm, temperatures = 30°C (Y2084) and 20°C (Vin13), oxygen saturation = 0% or 50%, and yeast inoculum concentration = ~8.00 Log CFU/mL. The maximum ethanol concentration achieved by Y2084 was 65.00 g/L. At 50% oxygen the fermentation time was 5 days, whilst at 0% oxygen the fermentation time was 11 days for Y2084. The maximum ethanol concentration achieved by Vin13 was 68.00 g/L. This concentration was obtained at 50% oxygen, and the fermentation time was 2 days. At 0% oxygen, Vin13 produced 31.00 g/L of ethanol within 2 days. Both yeast strains produced a higher glycerol concentration at 0% oxygen. Yeast viability counts showed a decrease at 0% oxygen and an increase at 50% oxygen of both yeast stains. Other analyses included measurement of carbon dioxide and oxygen gases, process monitoring of the fermentation conditions, and total organic carbon. Gas analysis showed that carbon dioxide increased in conjunction with ethanol production and oxygen decreased. Process monitoring depicted changes and stability of fermentation parameters during the process. Total organic carbon analysis revealed that aerobic fermentation (50% oxygen) was a more efficient process as a higher carbon recovery (95%) was achieved.

Bioprocess development for the production of an antifungal molecule by Bacillus licheniformis BC98

The optimization of process parameters for the production of an antifungal molecule produced by Bacillus licheniformis BC98 was carried out using novel statistical tools. The parameters studied were pH, temperature and agitation rate. Fed batch cultivations were carried out since the maximum production of the molecule was observed in the late log phase. The statistical design used allows the evaluation of the effects of several different process variables in a single batch. Data from several batches indicated that while the effects of two of the variable factors, viz., temperature and agitation rate, were significant at 95% confidence intervals, the agitation rate was most critical for the production of the molecule, and pH had no significant effect. The cultivation of the bacterium under optimized conditions (fed batch, 150 rpm, 32 degrees C, pH 5.8) resulted in a 30-fold increase compared with that under unoptimized conditions (shake flask, 100 rpm, 29 degrees C, pH 5.8) in the production of the antifungal molecule.