Kinetics of Saccharomyces cerevisiae Fermentation under Metal Ions Stress during Ethanol Production

Abstract

This research investigated the effects of inorganic compounds or metal ions (calcium ion, Ca2+; potassium ion, K+; magnesium ion, Mg2+) on ethanol production efficiency invertase, an enzyme produced by Saccharomyces cerevisiae, in sucrose solution, which was the substrate for yeast fermentation. The results showed that all metal ions (concentration 0.20 and 0.60 % (w/v)) acted as inhibitors on invertase activity in the order Ca2+ > K+ > Mg2+. Subsequently, these ions inhibited sugar conversion, reducing sucrose utilization and less glucose and fructose consumption based on the high content of remaining sugars in the culture medium. The reduction of the substrate was due to the consumption and an increased growth rate of S. cerevisiae, which all resulted in low efficiency of ethanol production and an increase in glycerol content. The glycerol content was increased due to yeast cells' developed mechanism or adaptation to enhance cell survival following metal ion contamination, especially from Ca2+ and K+; furthermore, the glycerol content significantly increased during the changed conditions, such as when the sugars were nearly all consumed. The kinetic parameters such as specific growth rate (µ-1), substrate consumption rate (Qs), and ethanol production of the research work were also undertaken. In conclusion, metal ion contamination in the sucrose substrate of yeast fermentation resulted in low efficiency of ethanol production, specific growth rate, and substrate consumption rate decrease with the Ca2+ ion (concentration 0.20 - 0.60 % (w/v)) acting more harshly as an inhibitor of ethanol production than the other ions, particularly where there was a high concentration of contamination.

Carbon-neutral synfuel production via continuous solar H2O and CO2 gasification of oil palm empty fruit bunch

“…Oil palm agricultural bio-waste is an abundant and widely available resource in many tropical regions, particularly in Southeast Asia [1]. Thailand is one of the major oil palm producers [2,3], and generates a significant quantity of oil palm waste (above 50 million tons in 2022), including empty fruit bunches (EFB), palm oil mill effluent, palm kernel shells, and palm fronds. Of this, the largest component of oil palm waste exceeding 19 million tons was EFB [4,5].…”

Clay Tiles Production Using Palm Ash, Spent Bleaching Earth, and Palm Fiber as Substitute Materials

“…The SBE amount excess 2 million caused after the manufacturing process to respond the worldwide demand of vegetable oil consumption [4]; these abundant wastes were usually eliminated with the direct landfill and resulted in the high cost to the manufacturer [3] and the environmental problem due to its complex components [5]. The palm oil industry caused the huge wastes of lignocellulosic materials such as fronds, trunk, empty fruit bunches, PF, and PA; the PF got more than 7,000,000 tonnes [6,7] from the both of oil palm plantation and palm oil production; the PA obtained after the combustion process of lignocellulosic materials such as empty fruit bunch and oil palm shell by almost 5% wt of these materials were converted into ash [8].…”