Área de Biotecnología Industrial, CIATEJ Centro de Investigación y Asistencia en Tecnología y Diseño del Estado de Jalisco, Av. Normalistas 800, Col. Colinas de la Normal, 44270, Guadalajara, Jal, Mexico.
Antonie Van Leeuwenhoek. 2012 Feb;101(2):195-204. doi: 10.1007/s10482-011-9622-x. Epub 2011 Jul 15.
This study aimed to improve the fermentation efficiency of Kloeckera africana K1, in tequila fermentations. We investigated organic and inorganic nitrogen source requirements in continuous K. africana fermentations fed with Agave tequilana juice. The addition of a mixture of 20 amino-acids greatly improved the fermentation efficiency of this yeast, increasing the consumption of reducing sugars and production of ethanol, compared with fermentations supplemented with ammonium sulfate. The preference of K. africana for each of the 20 amino-acids was further determined in batch fermentations and we found that asparagine supplementation increased K. africana biomass production, reducing sugar consumption and ethanol production (by 30, 36.7 and 45%, respectively) over fermentations supplemented with ammonium sulfate. Therefore, asparagine appears to overcome K. africana nutritional limitation in Agave juice. Surprisingly, K. africana produced a high concentration of ethanol. This contrasts to poor ethanol productivities reported for other non-Saccharomyces yeasts indicating a relatively high ethanol tolerance for the K. africana K1 strain. Kloeckera spp. strains are known to synthesize a wide variety of volatile compounds and we have shown that amino-acid supplements influenced the synthesis by K. africana of important metabolites involved in the bouquet of tequila. The findings of this study have revealed important nutritional limitations of non-Saccharomyces yeasts fermenting Agave tequilana juice, and have highlighted the potential of K. africana in tequila production processes.
本研究旨在提高非洲酒香酵母（Kloeckera africana）K1 在龙舌兰酒发酵中的发酵效率。我们研究了在连续发酵中，非洲酒香酵母利用龙舌兰汁作为氮源时对有机氮源和无机氮源的需求。与补充硫酸铵的发酵相比，添加 20 种氨基酸的混合物极大地提高了该酵母的发酵效率，增加了还原糖的消耗和乙醇的生产。在分批发酵中进一步确定了非洲酒香酵母对 20 种氨基酸中的每一种的偏好，我们发现天冬酰胺的补充增加了非洲酒香酵母的生物量生产、还原糖的消耗和乙醇的生产（分别减少了 30%、36.7%和 45%），而补充硫酸铵的发酵则减少了。因此，天冬酰胺似乎可以克服非洲酒香酵母在龙舌兰汁中的营养限制。令人惊讶的是，非洲酒香酵母产生了高浓度的乙醇。这与其他非酿酒酵母报道的较差乙醇生产效率形成对比，表明 K. africana K1 菌株对乙醇具有相对较高的耐受性。已知克勒克氏酵母（Kloeckera spp.）菌株可以合成多种挥发性化合物，我们已经表明，氨基酸补充剂影响了非洲酒香酵母合成与龙舌兰酒香气有关的重要代谢物。这项研究的结果揭示了非酿酒酵母发酵龙舌兰汁的重要营养限制，并强调了非洲酒香酵母在龙舌兰酒生产过程中的潜力。
