Program in Biotechnology, Faculty of Science, Chulalongkorn University, Bangkok, Thailand.
Biofuels By Biocatalysts Research Unit, Faculty of Science, Chulalongkorn University, Bangkok, Thailand.
World J Microbiol Biotechnol. 2023 Apr 17;39(6):159. doi: 10.1007/s11274-023-03602-7.
Acid-tolerant yeasts are one of the important keys to producing ethanol from acidic substrates, especially from molasses and agricultural waste. In this study, selected cultivars of yeasts isolated from a variety of locations such as botanical gardens in Thailand urban areas, which are often found highly polluted in the air such as carbon dioxide which is a cause of acid rain. There is limited information about how tolerant yeasts, are or their functional properties related to the environment. Yeast species were determined by using the 18S rDNA sequence guide. The level of acid tolerance was evaluated by adding to the culture medium lactic acid (300-900 mM), acetic acid (100-400 mM), and propionic acid (25-100 mM). 18S rDNA analysis has shown a %similarity of the nucleotide sequence higher than 98.65% compared to the database. Schwanniomyces etchellsii strains found in urban city soil were notable for their tolerance of lactic acid up to 100 mM. There are two main types of yeasts in overall acid tolerance: S. etchellsii, which is recognized as an osmotic pressure-resistant species that is highly resistant to fermentation inhibitors and produces ethanol; and Schizosaccharomyces pombe, which cell wall has been reported to be characterized by accumulation of α-(1,3)-glucan and malic acid can be used in metabolic pathways. The results show that S. pombe, isolated from rice paddy fields, can grow efficiently in acetic and propionic acid up to 400 mM and 100 mM, respectively. This species could be cultured in ethanol at a concentration of 12.5% (v/v). Moreover, it presented high ethanol and acetic acid production of 14.5-15.9 g/L and 7-10 g/L, respectively, with or without acidic conditions. In comparison, S. etchellsii, isolated from the botanical garden soil, which is grown in acetic, propionic, and lactic acid, was also indicated to be an organic acid-tolerant species.
耐酸酵母是从酸性基质中生产乙醇的重要关键之一，特别是从糖蜜和农业废物中。在这项研究中，从泰国植物园等各种地点分离出的酵母选定品种，这些地点的空气通常受到高度污染，如二氧化碳，这是酸雨的一个成因。关于酵母的耐受性及其与环境相关的功能特性，信息有限。使用 18S rDNA 序列指南确定酵母种类。通过向培养基中添加乳酸（300-900 mM）、乙酸（100-400 mM）和丙酸（25-100 mM）来评估耐酸水平。18S rDNA 分析显示，核苷酸序列的 %相似度高于数据库中的 98.65%。在城市土壤中发现的 Schwanniomyces etchellsii 菌株因其耐受高达 100 mM 的乳酸而引人注目。耐酸的主要酵母有两种类型：S. etchellsii，它被认为是一种耐渗透压的物种，对发酵抑制剂具有高度抗性，并产生乙醇；Schizosaccharomyces pombe，其细胞壁已被报道以积累α-（1,3）-葡聚糖和苹果酸为特征，可以用于代谢途径。结果表明，从稻田中分离出的 S. pombe 可以在高达 400 mM 和 100 mM 的乙酸和丙酸中高效生长。该物种可以在 12.5%（v/v）的乙醇浓度下培养。此外，它在有或没有酸性条件下分别呈现出 14.5-15.9 g/L 和 7-10 g/L 的高乙醇和乙酸产量。相比之下，从植物园土壤中分离出的 S. etchellsii 也被证明是一种耐有机酸的物种，它可以在乙酸、丙酸和乳酸中生长。
