Palakawong Na Ayutthaya Pakathamon, Charoenrat Theppanya, Krusong Warawut, Pornpukdeewattana Soisuda
1Division of Fermentation Technology, Faculty of Agro-Industry, King Mongkut's Institute of Technology Ladkrabang, Bangkok, 10520 Thailand.
2Department of Biotechnology, Faculty of Science and Technology, Thammasat University (Rangsit Center), Pathum Thani, 12120 Thailand.
3 Biotech. 2019 Mar;9(3):76. doi: 10.1007/s13205-019-1607-x. Epub 2019 Feb 11.
Large amount of cassava pulp is produced as by-product of industrial tapioca production. The value-added process of this low-cost waste is to use it as a substrate for bioethanol production. However, during the pulp pretreatment by acidification combined with steam explosion, many yeast inhibitors including acetic acid, formic acid, levulinic acid, furfural and 5-hydroxymethylfurfural are generated and these compounds have negative effects on the subsequent fermentation step. Therefore, the objective of this study was to investigate whether the repeated cultures of SC90 could alleviate this problem. To obtain the inhibitor tolerable cells, the repeated culture was performed by growing yeast cells to a specific growth rate () of 0.22 h or higher (80% of the in control) and then transferring them to progressively higher concentrations of hydrolysate ranging from 20 to 100% (v/v). The results showed a tendency of longer lag phase as well as time to reach maximum cell number ( ) with an increase in hydrolysate concentration. However, the repeated culture at the same hydrolysate concentration could shorten both lag period and . Interestingly, the growth and fermentation efficiency of adapted cells in 100% hydrolysate were significantly higher ( ≤ 0.05) than those of non-adapted cells by 38% and 27%, respectively.
大量木薯渣作为工业木薯淀粉生产的副产品产生。这种低成本废弃物的增值过程是将其用作生物乙醇生产的底物。然而，在通过酸化结合蒸汽爆破进行的木薯渣预处理过程中，会产生许多酵母抑制剂，包括乙酸、甲酸、乙酰丙酸、糠醛和5-羟甲基糠醛，这些化合物对后续的发酵步骤有负面影响。因此，本研究的目的是调查酿酒酵母SC90的重复培养是否可以缓解这个问题。为了获得耐受抑制剂的细胞，通过将酵母细胞培养至特定生长速率（μ）为0.22 h⁻¹或更高（为对照中μ的80%），然后将它们转移到浓度逐渐升高的水解产物中，水解产物浓度范围为20%至100%（v/v），进行重复培养。结果表明，随着水解产物浓度的增加，延迟期以及达到最大细胞数（Xmax）的时间有延长的趋势。然而，在相同水解产物浓度下进行重复培养可以缩短延迟期和Xmax。有趣的是，适应细胞在100%水解产物中的生长和发酵效率分别比未适应细胞显著提高（P≤0.05）38%和27%。
