Effect of micro-aeration on the growth of Candida pseudotropicalis and production of ethanol during batch fermentation of cheese whey

Oxygen Effects in Anaerobic Digestion – A Review

“…Tango and Ghaly [89] studied the effects of limited aeration on the lactic acid production from cheese whey using anaerobic bacteria specie Lactobacillus helveticus. The findings are very similar to those by Ghaly and El-Taweel [88]. Limited aeration significantly improved the specific growth rate and enhanced the lactic acid yield while reducing the lag period of growth.…”

“…An associated BOD (biological oxygen demand) test also revealed that aerobic degradation of MEA is possible with faster kinetics and also with higher amine concentrations compared to anaerobic degradation [106]. The hypothesis of Tango and Ghaly [89] and Ghaly and El-Taweel [88] that enhanced cell yields by aeration lead to stronger cultures which are more tolerable for substrate inhibition, may also be relevant in explaining these observations. Some compounds or micro-pollutants inducing a toxic effect on one group of organisms can be used as a substrate for other organisms.…”

“…As reported by Ghaly and El-Taweel [88], oxygen at very low concentrations is required by anaerobic yeast cultures to synthesize certain lipids needed to build cell walls. A similar finding was reported by Tango and Ghaly [89].…”

“…They highlighted the need of determining the optimum oxygen limited condition by using a unit-less parameter like respiratory quotient which is defined as the ratio between the CO 2 evolution rate and the oxygen utilization rate. Experimenting on the effects of limited aeration on the growth of yeast Candida pseudotropicalis and production of ethanol during batch fermentation of cheese whey, Ghaly and El-Taweel [88] showed that increasing the rate of limited aeration decreased the lag period of growth and increased the specific growth rate, maximum cell number and also the substrate utilization rate. Meanwhile, the increased limited aeration increased the ethanol yield up to a certain aeration rate (up to 0.1 vvm.…”

“…Tango and Ghaly [89] and Ghaly and El-Taweel [88] demonstrated that the limited aeration greatly affects the cell growth. At a given substrate concentration, increasing aeration resulted in a higher specific growth rate, hence the culture became more tolerant against substrate inhibition.…”