The interest for sweet sorghum and sweet pearl millet use as potential feedstocks for bioethanol production has markedly increased in the last few years due to the high concentration in fermentable carbohydrates in their juice. The bottleneck of this production is the carbohydrate extraction process that needs to be optimized. The main objective of this study was therefore to determine the effect of operating conditions on water-soluble carbohydrate (WSC) extraction from the biomass of both species. For this purpose, two chopping modes of the biomass (coarse and fine) were investigated. Furthermore, the biomass was subjected to a second pressing after impregnation with water. In this context, the effects of four water:bagasse ratios (0.5, 1, 1.5, and 2) and three water temperatures (25, 45, and 65 °C) were evaluated. The initial biomass WSC concentration was 180 g kg⁻¹ DM for sweet sorghum and 125.7 g kg⁻¹ DM for sweet pearl millet. After the first pressing, these concentrations decreased by 63 and 56%, respectively. For the second pressing, the efficiency of WSC extraction was more influenced by the water:bagasse ratio than by the chopping mode and the water temperature. For an economic and energetic sustainable extraction process of carbohydrates, a coarse chopping, and a second pressing after impregnation with a water:bagasse ratio of 1 at 25 °C are therefore recommended to improve residual carbohydrate extraction. Under these conditions, the WSC extraction yields reached 83 and 78% for sweet sorghum and sweet pearl millet biomass, respectively.

中文翻译：

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甜高粱和甜珍珠粟生物质中水溶性碳水化合物的提取工艺优化

近几年来，由于甜高粱和甜珍珠粟作为果汁中可发酵碳水化合物的浓度很高，因此作为生物乙醇生产的潜在原料的兴趣已显着增加。该生产的瓶颈是需要优化的碳水化合物提取过程。因此，本研究的主要目的是确定操作条件对从两种生物质中提取水溶性碳水化合物（WSC）的影响。为此，研究了生物质的两种切碎模式（粗和细）。此外，在用水浸渍之后，对生物质进行第二次加压。在这种情况下，评估了四种水：蔗渣比（0.5、1、1.5和2）和三种水温（25、45和65℃）的影响。^-1 DM甜高粱和125.7克千克^-1 DM甜珍珠粟。第一次按压后，这些浓度分别降低了63％和56％。对于第二次压榨，WSC提取效率受水：蔗渣比的影响更大，而不是受斩波模式和水温的影响。因此，对于经济，充满活力的可持续碳水化合物提取工艺，建议进行粗碎，然后在25°C下以1的水：蔗渣比率浸渍后进行二次压榨，以改善残留碳水化合物的提取。在这些条件下，甜高粱和甜珍珠粟生物量的WSC提取率分别达到83％和78％。