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Abstract：
The energy crisis triggers the use of energy sources that are renewable, such as biomass made from lignocellulosic materials, to produce various chemical compounds for food ingredients and biofuel. The efficient conversion of lignocellulosic biomass into products with added value involves the activity of microorganisms, such as yeasts. For the conversion, microorganisms must be able to use various sugars in lignocellulosic biomass, including pentose sugars, especially xylose. This study aims to isolate xylose-utilizing yeasts and analyze their fermentation activity to produce xylitol and ethanol, as well as their ability to grow in liquid hydrolysate produced from pretreated lignocellulosic biomass. Nineteen yeast isolates could grow on solid and liquid media using solely xylose as a carbon source. All isolates can grow in a xylose medium with incubation at 30 °C, 37 °C, 42 °C, and 45 °C. Six isolates, namely SLI (1), SL3, SL6, SL7, R5, and OPT4B, were chosen based on their considerable growth and high xylose consumption rate in a medium with 50 g/L xylose with incubation at 30 °C for 48 h. Four isolates tested, namely SLI (1), SL6, SL7, and R5, can produce xylitol in media containing xylose carbon sources. The concentration of xylitol produced was determined using high-pressure liquid chromatography (HPLC), and the results ranged from 5.0 to 6.0 g/L. Five isolates tested, namely SLI (1), SL6, SL3, R5, and OPT4B, can produce ethanol. The ethanol content produced was determined using gas chromatography (GC), with concentrations ranging from 0.85 to 1.34 g/L. Three isolates, namely SL1(1), R5, and SL6, were able to produce xylitol and ethanol from xylose as carbon sources and were also able to grow on liquid hydrolyzate from pretreated oil palm trunk waste with the subcritical water method. The three isolates were further analyzed using the 18S rDNA sequence to identify the species and confirm their phylogenetic position. Identification based on DNA sequence analysis revealed that isolates SL1(1) and R5 were Pichia kudriavzevii, while isolate SL6 was Candida xylopsoci. The yeast strains isolated from this study could potentially be used for the bioconversion process of lignocellulosic biomass waste to produce value-added derivative products.
摘要：
能源危机引发了可再生能源的使用，例如由木质纤维素材料制成的生物质，生产用于食品配料和生物燃料的各种化合物。将木质纤维素生物质有效转化为具有附加值的产品涉及微生物的活性，如酵母。对于转换，微生物必须能够在木质纤维素生物质中使用各种糖，包括戊糖，尤其是木糖.本研究旨在分离利用木糖的酵母，并分析其发酵生产木糖醇和乙醇的活性，以及它们在预处理的木质纤维素生物质产生的液体水解产物中生长的能力。仅使用木糖作为碳源，可以在固体和液体培养基上生长19种酵母分离物。所有分离物可以在30°C孵育的木糖培养基中生长，37°C,42°C,45°C六个分离株，即SLI(1)，SL3、SL6、SL7、R5和OPT4B，根据其在50g/L木糖培养基中的可观生长和高木糖消耗率进行选择，并在30°C孵育48小时。测试了四个分离株，即SLI(1)，SL6、SL7和R5可以在含有木糖碳源的培养基中产生木糖醇。使用高压液相色谱（HPLC）确定产生的木糖醇的浓度，结果范围为5.0至6.0g/L。测试了五个分离株，即SLI(1)，SL6、SL3、R5和OPT4B，可以生产乙醇。使用气相色谱法(GC)测定产生的乙醇含量,浓度范围为0.85至1.34g/L。三个隔离，即SL1(1)，R5和SL6能够从木糖作为碳源生产木糖醇和乙醇，并且还能够通过亚临界水方法在预处理的油棕干废物的液体水解产物上生长。使用18SrDNA序列进一步分析了这三个分离株，以鉴定物种并确认其系统发育位置。基于DNA序列分析的鉴定表明，分离株SL1（1）和R5为毕赤酵母，而分离株SL6为木偶假丝酵母。从这项研究中分离出的酵母菌株可潜在地用于木质纤维素生物质废物的生物转化过程，以产生增值的衍生产品。
