Selection and Characterization of Potential Baker’s Yeast from Indigenous Resources of Nepal

Abstract

The study aims to isolate the yeast strains that could be used effectively as baker's yeast and compare them with the commercial baker's yeast available in the market of Nepal. A total of 10 samples including locally available sources like fruits, Murcha, and a local tree "Dar" were collected from different localities of Bhaktapur, Kavre, and Syangja districts of Nepal, respectively. Following enrichment and fermentation of the samples, 26 yeast strains were isolated using selective medium Wallerstein Laboratory Nutrient Agar. From the differential tests which included morphological and microscopic observation and physiological and biochemical characterization such as nitrate reduction and lactose utilization tests, 8 strains were selected as possible Saccharomyces strain. The selected strains were further assessed for their efficient leavening ability by tests such as ethanol tolerance, osmotolerance, invertase test, and stress exclusion test. The three most potent strains ENG, MUR3B, and SUG1 isolated from grape, Murcha, and sugarcane, respectively, were used in the fermentation and baking of dough. These strains also carried a possibility of being used as industrial baker's yeast.

Characterization of wild type yeast isolated from Sabah soil for environmental friendly biofuel production

“…The capability of fermentation was assessed by observing the colour change in the medium after the incubation. Sugar fermentation was observed by the colour change from red to yellow due to acid production [16].…”

Potential test of endophytic yeast from sweet oranges (Citrus sinensis L.) as leavening agent for bread

“…Then it was incubated at 27 o C for 7 days. The fermentation medium was put in a test tube equipped with a Durham tube [6]. A positive reaction for fermentation was indicated by a change in the media from red to pink followed by the formation of bubbles in the Durham tube.…”

“…Yeast has four roles in the bread-making process, namely to increase the volume of the dough due to the formation of carbon dioxide during the fermentation process, to develop the structure and texture of the dough due to stretching by the expansion of CO2 gas bubbles, to improve the taste and to add some nutritional value to the bread [4]. Yeast for bread developers must have basic requirements, namely being able to survive in conditions that have high ethanol levels between 10%-15%, and tolerance to various temperature conditions of 25 o C, 30 o C, 37 o C dan 45 o C [6]. Good yeast as a developer Bread must be able to form flocculants or floc deposits in the flocculation process and not produce hydrogen sulfide (H2S) gas which is a compound that forms a foul smell and bad taste in bread processing [2].…”

Improving SCOBY starter using co-culture of tapai and bakery yeast

“…Otherwise, commercial yeast can be obtained from baker's yeast and tapai yeast. Other research has reported that tapai yeast contains molds, such as Rhizopus oryzae, Monilesaurus rouxii, Aspergillus orzae, Saccharomyces cervisiae, Endomycopsis burtonii, Pediococcus pentosaceus, Hansenula anomala, Candida krusei, Candida magnoliae (Chiang et al 2006;Rahman et al 2018), whereas baker's yeast contains Saccharomyces cerevisiae (Karki et al 2017). Kumoro et al (2012) used baker's yeast in the production of jackfruit wine.…”