Yeasts involved in the spontaneous fermentation of traditional beverages like chicha (indigenous Andean beer) may have the potential to be used as starter cultures to improve the quality and microbiological safety of these products, but also as non-conventional alternatives to other food alcoholic fermentations. In this research, we isolated, identified and characterised yeast strains from four Ecuadorian chichas made by using four different raw materials: rice (RC), oat (OC), grape (GC) and a mixture of seven corn varieties (yamor, YC). Finally, 254 yeast isolates were obtained and identified by molecular methods. Eleven yeast genera and 16 yeast species were identified with relatively few isolates belonging to Saccharomyces cerevisiae (9.1% belonging to 6 strains) and Torulaspora delbrueckii (18.6% belonging to 2 strains). In order to select good candidates for fermentative starter production, different analyses were performed. The results of the stress response tests showed a wide variability between species and strains, and identified some yeasts displaying high stress tolerance, similarly to commercial wine strains. Amylase production was screened as being indicative of the capacity to degrade and ferment starch-rich substrates. A Cryptococcus sp. isolate showed the highest amylase activity. The growth rate and fermentative capacity in molasses medium was measured for three S. cerevisiae, T. delbrueckii and Candida sp. strains as tests for yield and performance in biomass production. Based on their excellent behaviour, three S. cerevisiae strains and one T. delbrueckii strain were selected for further analyses, including dehydration tolerance and invertase activity as additional desired traits for chicha starters. All the S. cerevisiae strains exhibited high invertase activity and one also displayed high resistance to dehydration. The yeasts selected in this study can thus be suitably used as dry starters for the microbiologically controlled production of traditional beverages, and also for other alcoholic fermentations.

中文翻译：

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厄瓜多尔奇卡酵母在食品工业中作为酒精发酵起子的性能评估。

涉及传统饮料（例如chicha（安第斯山脉的本地啤酒））自发发酵的酵母可能有潜力用作发酵剂，以提高这些产品的质量和微生物安全性，也可以作为其他非常规食品酒精发酵的替代品。在这项研究中，我们从四种厄瓜多尔奇奇酵母中分离，鉴定和鉴定了酵母菌株，这些奇奇奇豆使用四种不同的原料制成：大米（RC），燕麦（OC），葡萄（GC）和七个玉米品种的混合物（yamor，YC） 。最终，获得了254种酵母分离物，并通过分子方法进行了鉴定。鉴定出11个酵母属和16个酵母种类，其中相对少的分离物属于酿酒酵母（9.1％，属于6个菌株）和杜氏假单胞菌（18.6％，属于2个菌株）。为了选择发酵发酵剂生产的良好候选者，进行了不同的分析。压力响应测试的结果表明，品种和菌株之间存在很大的差异，并且与商业葡萄酒菌株相似，鉴定出一些酵母具有较高的抗逆性。筛选淀粉酶的产生以指示降解和发酵富含淀粉的底物的能力。隐球菌 分离株显示出最高的淀粉酶活性。测定了三个酿酒酵母，德氏布鲁氏菌和假丝酵母菌在糖蜜培养基中的生长速率和发酵能力。菌株作为生物量生产中产量和性能的测试。根据其优异的性能，选择了3株酿酒酵母和1株T. delbrueckii菌株进行进一步分析，包括脱水耐受性和转化酶活性，这是chicha发酵剂的其他所需特性。所有酿酒酵母菌株均表现出高转化酶活性，并且还表现出对脱水的高抗性。因此，在这项研究中选择的酵母可以适合用作微生物发酵生产传统饮料以及其他酒精发酵的干发酵剂。