Enhanced Bioethanol Production from Potato Peel Waste Via Consolidated Bioprocessing with Statistically Optimized Medium

Abstract

In this study, an extensive screening was undertaken to isolate some amylolytic microorganisms capable of producing bioethanol from starchy biomass through Consolidated Bioprocessing (CBP). A total of 28 amylolytic microorganisms were isolated, from which 5 isolates were selected based on high α-amylase and glucoamylase activities and identified as Candida wangnamkhiaoensis, Hyphopichia pseudoburtonii (2 isolates), Wickerhamia sp., and Streptomyces drozdowiczii based on 26S rDNA and 16S rDNA sequencing. Wickerhamia sp. showed the highest ethanol production (30.4 g/L) with fermentation yield of 0.3 g ethanol/g starch. Then, a low cost starchy waste, potato peel waste (PPW) was used as a carbon source to produce ethanol by Wickerhamia sp. Finally, in order to obtain maximum ethanol production from PPW, a fermentation medium was statistically designed. The effect of various medium ingredients was evaluated initially by Plackett-Burman design (PBD), where malt extracts, tryptone, and KHPO showed significantly positive effect (p value < 0.05). Using Response Surface Modeling (RSM), 40 g/L (dry basis) PPW and 25 g/L malt extract were found optimum and yielded 21.7 g/L ethanol. This study strongly suggests Wickerhamia sp. as a promising candidate for bioethanol production from starchy biomass, in particular, PPW through CBP.

Bioconversion of Potatoes to Bioethanol

“…This may be due to the fact that the coculture of AN and α-amylase prevents the accumulation of inhibitors, accordingly improves the conversion of sugars to bioethanol. This observation was recorded by Abouzied and Reddy [12], and was also confirmed by Kongkiattikajorn and Sornvoraweat [21,[22][23][24]. Figure 11.…”

Enhancing Astaxanthin Biosynthesis by Rhodosporidium toruloides Mutants and Optimization of Medium Compositions Using Response Surface Methodology

“…The result showed that malt extract exhibited a significant effect on astaxanthin synthesis (p < 0.05) while peptone had insignificant effect (p > 0.05) in the evaluated range (Table 6). Studies have reported that the nitrogen level of malt extract may differ from 1.4% to 1.8% which may be insufficient in itself [49], but when mixed with another nitrogen source (peptone in this study), it was observed to be essential for R. toruloides to synthesize astaxanthin. However, a further increase in malt extract resulted in a decline in astaxanthin accumulation due to the negative effect of high levels of nitrogen on the astaxanthin biosynthesis [2].…”

“…At any glucose concentration, the astaxanthin yield considerably increased with increasing amount of malt extract. This might be because malt extract plays an important role as a complex of nitrogen and carbon source, which promotes the growth of yeast, resulting in higher astaxanthin yield [49][50][51]. In this work, malt extract was used as an additional nitrogen source for the cultivation of R. toruloides.…”

Development of high temperature simultaneous saccharification and fermentation by thermosensitive Saccharomyces cerevisiae and Bacillus amyloliquefaciens

“…The reduced enzyme production may form less reducing sugar and lower ethanol, reciprocally. It is well-known that Saccharomyces cerevisiae lacks starch degrading enzymes 29 . A possible reason of higher ethanol production by co-cultures can be the ability of amylolytic strain (C-7) to convert starch polysaccharides into simple sugar units through saccharification.…”