Department of Food Science and Technology, Phaff Yeast Culture Collection, University of California Davis, Davis, CA, United States of America.
Department of Biological and Agricultural Engineering, University of California Davis, Davis, CA, United States of America.
PLoS One. 2023 Nov 15;18(11):e0293085. doi: 10.1371/journal.pone.0293085. eCollection 2023.
Animal feed ingredients, especially those abundant in high quality protein, are the most expensive component of livestock production. Sustainable alternative feedstocks may be sourced from abundant, low value agricultural byproducts. California almond production generates nearly 3 Mtons of biomass per year with about 50% in the form of hulls. Almond hulls are a low-value byproduct currently used primarily for animal feed for dairy cattle. However, the protein and essential amino acid content are low, at ~30% d.b.. The purpose of this study was to improve the protein content and quality using yeast. To achieve this, the almond hulls were liquefied to liberate soluble and structural sugars. A multi-phase screening approach was used to identify yeasts that can consume a large proportion of the sugars in almond hulls while accumulating high concentrations of amino acids essential for livestock feed. Compositional analysis showed that almond hulls are rich in polygalacturonic acid (pectin) and soluble sucrose. A pectinase-assisted process was optimized to liquefy and release soluble sugars from almond hulls. The resulting almond hull slurry containing solubilized sugars was subsequently used to grow high-protein yeasts that could consume nutrients in almond hulls while accumulating high concentrations of high-quality protein rich in essential amino acids needed for livestock feed, yielding a process that would produce 72 mg protein/g almond hull. Further work is needed to achieve conversion of galacturonic acid to yeast cell biomass.
动物饲料成分，尤其是那些富含高质量蛋白质的成分，是畜牧业生产中最昂贵的组成部分。可持续的替代饲料来源可以从丰富、低价值的农业副产品中获取。加利福尼亚州杏仁生产每年产生近 300 万吨生物质，其中约 50%为壳。杏仁壳是一种低价值的副产品，目前主要用于奶牛的动物饲料。然而，其蛋白质和必需氨基酸含量较低，约为 30%（干基）。本研究旨在使用酵母提高蛋白质含量和质量。为此，杏仁壳被液化以释放可溶和结构糖。采用多相筛选方法来鉴定能够消耗杏仁壳中大量糖并积累对牲畜饲料至关重要的氨基酸的酵母。成分分析表明，杏仁壳富含多聚半乳糖醛酸（果胶）和可溶性蔗糖。优化了果胶酶辅助工艺，以液化和释放杏仁壳中的可溶性糖。随后，将得到的含有溶解糖的杏仁壳浆用于培养高蛋白酵母，这些酵母可以消耗杏仁壳中的营养物质，同时积累富含牲畜饲料所需必需氨基酸的高质量蛋白质，从而实现每克杏仁壳产生 72 毫克蛋白质的工艺。需要进一步的工作来实现半乳糖醛酸到酵母细胞生物质的转化。
