Department of Chemical, Biomolecular, and Corrosion Engineering, The University of Akron, Akron, OH, USA.
ideaCHEM, Inc., Rapid City, SD, USA.
Enzyme Microb Technol. 2023 Oct;170:110302. doi: 10.1016/j.enzmictec.2023.110302. Epub 2023 Aug 6.
Soybean processing generates huge amounts of soy molasses that can support biorefinery but require development of waste-to-value conversion technologies. Here, soy molasses processing by Aspergillus niger enzymes was studied to optimize the conversion of oligosaccharides to monomeric sugars as ready fermentation feedstock. The effects of pH and temperature were first investigated using fixed enzyme composition and loading. pH, in the tested 3.0-6.5 range, significantly affected hydrolysis particularly in galactose release. The hydrolysis was fastest at pH 4.8 and 60 °C although the 48-h sugar (glucose, fructose, and galactose) yields were similar at pH 4.8 and 5.7, and 50 and 60 °C. Study was next made at these favorable pH and temperatures using different enzyme compositions and loadings. Glucose and fructose were effectively released, reaching ∼100 % yields in 24-48 h by most of the enzymes and loadings evaluated. Galactose production was less effective and varied significantly with the pH-temperature condition and enzyme loading and composition. Mechanistic evaluation suggested formation and accumulation of galactose disaccharide, whose slow hydrolysis was rate-limiting in the systems with complete glucose and fructose releases but low galactose yields. Model equations were developed to describe the kinetic sugar-release profiles and make technoeconomic analysis, which showed that a process of lower enzyme loading, while requiring longer duration, is more economical within the analyzed range of 5-50 (U α-galactosidase/g molasses). With 5 (U/g) loading, the total cost is about 30 % lower at 60 °C-pH 5.7 than 50 °C-pH 4.8. The α-galactosidase-to-sucrase ratio plays a less significant role in affecting the overall process cost.
大豆加工产生大量的大豆糖蜜，可以支持生物炼制，但需要开发废物转化为价值的技术。在这里，研究了黑曲霉酶对大豆糖蜜的加工，以优化低聚糖转化为单体糖作为现成的发酵原料。首先使用固定的酶组成和负载研究了 pH 和温度的影响。在测试的 3.0-6.5 范围内，pH 值显著影响水解作用，特别是在半乳糖释放方面。水解在 pH4.8 和 60°C 时最快，尽管在 pH4.8 和 5.7 以及 50 和 60°C 时 48 小时糖（葡萄糖、果糖和半乳糖）的产率相似。然后在这些有利的 pH 值和温度下使用不同的酶组成和负载进行研究。葡萄糖和果糖被有效地释放，大多数评估的酶和负载在 24-48 小时内达到约 100%的产率。半乳糖的产量较低，且受 pH-温度条件、酶负载和组成的影响显著。机理评估表明，半乳糖二糖的形成和积累，其缓慢水解是在完全释放葡萄糖和果糖但半乳糖产量较低的系统中限速步骤。建立了模型方程来描述动力学糖释放曲线，并进行技术经济分析，结果表明在分析的 5-50（Uα-半乳糖苷酶/g 糖蜜）范围内，较低酶负载的过程虽然需要更长的时间，但在经济上更具优势。在 5（U/g）负载下，60°C-pH5.7 的总成本比 50°C-pH4.8 低约 30%。α-半乳糖苷酶-蔗糖酶的比例在影响整个过程成本方面的作用较小。
