Abstract
AbstractA bench scale submerged fermentation process was used to bioethanol produce using sugar beet molasses andSaccharomyces cerevisiae, as substrate and microbial strain, respectively. Effects of selenium amount on growth ofS. cerevisiaeand bioethanol production were evaluated. The obtained results indicated that growth ofS. cerevisiae(manifested as turbidity intensity) in the samples containing 0, 5, 10, 15, 20 and 25 μg sodium selenite, during aerobic process, was 0.1707, 0.1678, 0.1679, 0.1664, 0.1627 and 0.160% a.u./h (after 14 h incubation), respectively. Statistical analysis based on compression test indicated that there were insignificant (p > 0.05) differences between growth rate of the yeast in the fermented samples containingS. cerevisiaeand 5 to 25 μg selenium salt. Response surface methodology was utilized to evaluate effects of two fermentation parameters namely, amount of selenium (5-25 μg) and substrate brix (10-25°Bx) on the concentration (g/L) of produced bioethanol. Obtained results revealed that maximum bioethanol concentration (55 g/L) was achieved using 15 μg selenium and molasses with 25°Bx. Furthermore, results have also indicated that, without using selenium and using molasses with 25°Bx, bioethanol with concentration of 29 g/L was produced.
Highlights
Glutamate in the yeast, can decrease the energy generation and fermentation rate, by altering the mitochondrial structure and dynamics, which those negatively impacts can be prevented by organic selenium such as seleno-cysteine which that is resulted during bio-transformation of inorganic selenium using yeasts such as S. cerevisiae [12,14]
Other study indicated that contents of organic selenium in the S. cerevisiae during fermentation process to produce bioethanol, increased with the increase in selenium concentration up to 2 μg/mL followed by a gradual decrease after 24 h of incubation
The obtained results indicated that growth rate (manifested as turbidity intensity (% a.u.)) of the S. cerevisiae in the samples including, 0, 5, 10, 15, 20 and 25 μg selenium was 0.1707, 0.1678, 0.1679, 0.1664, 0.1627 and 0.160% a.u./h, respectively
Summary
Statistical analysis based on compressiopnaitresAt, iAn∗diocfa-diaagdodniatilviezsa,belnezFym-liense, aanr tmibaioptsicos,noVrg,aenaicchacoidfsw, bhiiocfhuealcatnsdon an eigenb ted that there were insignificant (p > 0.0ir5r)edduifcfeirbelnectersidiabgioognaasl[f1a].shion Such a pair is called a Leonard pair Other study indicated that contents of organic selenium in the S. cerevisiae during fermentation process to produce bioethanol, increased with the increase in selenium concentration up to 2 μg/mL followed by a gradual decrease after 24 h of incubation. It reveals that organic selenium has low bioavailability [16]. The main objectives of the present study were to i) evaluate the effect of selenium on the concentration of produced bioethanol, ii) optimize submerged fermentation parameters namely substrate and selenium concentrations to achieve bioethanol with highest concentration, and iii) compare concentration of produced bioethanol, between cultivation made with and without selenium
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