Yeast strains tolerant to a wide range of stress conditions are needed for the production of bioethanol from substrates rich in sugar. In our earlier research findings, Meyerozyma caribbica isolate MJTm3 (OM329077) demonstrated remarkable stress tolerance and fermentative activity. The present study aimed to optimize six fermentation parameters to generate conducive fermentation conditions for ethanol production by M. caribbica isolate MJTm3. The response surface method (RSM) based on central composite design (CCD) was employed to optimize process conditions for higher bioethanol yield. The optimization process was carried out based on six independent parameters, namely temperature (25–35 °C), pH (5.5–6.5), inoculum size (10–20% (v/v)), molasses concentration (25–35 (w/v)), mixing rate (110–150 rpm), and incubation period (48–72-h). Analysis of ethanol concentration was done by HPLC equipped with a UV detector. The optimal conditions of the parameters resulting in a maximum predicted ethanol yield were as follows: pH 5.5, an inoculum size of 20%, a molasses concentration of 25 °Bx, a temperature of 30 °C, an incubation period of 72-h, and a mixing rate of 160 revolutions per minute (rpm). Using the above optimum conditions, the model predicted a bioethanol yield of 79%, 92% of the theoretical yield, a bioethanol concentration of 49 g L−1, and a productivity of 0.68 g L−1 h−1. A batch fermentation experiment was carried out to validate the predicted values and resulted in a bioethanol yield of 86%, 95% of theoretical yield, a bioethanol concentration of 56 g L−1, and productivity of 0.78 g L−1 h−1. On the other hand, the surface plot analysis revealed that the synergistic effect of the molasses concentration and the mixing rate were vital to achieving the highest bioethanol yield. These values suggested that the RSM with CCD was an effective method in producing the highest possible output of bioethanol from molasses in actual operation. The study confirmed the potential of using M. caribbica isolate MJTm3 for bioethanol production from sugarcane molasses under the abovementioned optimal fermentation conditions.

中文翻译：

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使用 Meyerozyma caribbica 分离株 MJTm3 通过响应面法优化甘蔗糖蜜的生物乙醇生产

从富含糖的底物生产生物乙醇需要能够耐受各种胁迫条件的酵母菌株。在我们早期的研究结果中，Meyerozyma caribbica 分离株 MJTm3 (OM329077) 表现出显着的胁迫耐受性和发酵活性。本研究旨在优化六个发酵参数，以产生有利于 M. caribbica 分离株 MJTm3 生产乙醇的发酵条件。采用基于中心复合设计 (CCD) 的响应面法 (RSM) 来优化工艺条件以提高生物乙醇产量。优化过程基于六个独立参数进行，即温度 (25–35 °C)、pH (5.5–6.5)、接种量 (10–20% (v/v))、糖蜜浓度 (25–35 ( w / v）），混合速率（110-150 rpm）和孵育期（48-72-h）。乙醇浓度的分析通过配备有UV检测器的HPLC进行。导致最大预测乙醇产量的参数的最佳条件如下：pH 5.5，接种量为 20％，糖蜜浓度为 25°Bx，温度为 30°C，孵育期为 72 小时，混合速率为每分钟 160 转 (rpm)。使用上述最佳条件，该模型预测生物乙醇产量为 79%，理论产量的 92%，生物乙醇浓度为 49 g L-1，生产率为 0.68 g L-1 h-1。进行了分批发酵实验以验证预测值，结果生物乙醇产量为 86%，理论产量的 95%，生物乙醇浓度为 56 g L-1，生产率为 0.78 g L-1 h-1。另一方面，曲面图分析表明，糖蜜浓度和混合速率的协同效应对于实现最高生物乙醇产量至关重要。这些值表明，带有 CCD 的 RSM 是在实际操作中从糖蜜中生产尽可能高的生物乙醇产量的有效方法。该研究证实了在上述最佳发酵条件下使用 M. caribbica 分离物 MJTm3 从甘蔗糖蜜生产生物乙醇的潜力。