[P004] Poster

1:00 PM - 1:50 PM JST(4:00 AM - 4:50 AM UTC)

[P02-174] Screening of wild yeasts suitable for beer brewing

○Takuto NAKASHIMA¹, Yumiko Yoshizaki¹, Taiki Futagami¹, Hisanori Tamaki¹, Kazunori Takamine¹ (1. Kagoshima University (Japan))

Keywords:

wild yeast,craft beer,fermentation,Saccharomyces cerevisiae

Kagoshima Prefecture is well known as a major production center of honkaku shochu and interest in craft beer utilizing local resources has grown considerably in recent years, with several breweries now established across the prefecture. In the craft beer industry, differentiation through region-specific fruit adjuncts has become the prevailing strategy, while yeast exploration has been insufficiently pursued owing to technical and cost-related constraints.In the present study, conducted in collaboration with a local enterprise in Kagoshima Prefecture, we focused on a natural forest in central Kagoshima City with the aim of isolating and selecting wild yeasts inhabiting this environment for application in craft beer brewing. Samples were collected from the bark and branches of native trees and cultured in YPM medium a formulation approximating wort composition at 30℃ for 2-3 days. Strains exhibiting CO2 production were isolated and identified by genetic analysis. Five strains displaying vigorous fermentation activity were selected for small-scale brewing trials, in which each isolate and a commercial brewing yeast (control) were inoculated into 300 mL of wort and fermented at 20℃ for 7 days, with daily weight loss recorded as a proxy for fermentative activity. Following fermentation, alcohol content was determined by distillation and sugar assimilation was assessed by HPLC. Of the 100samples collected, 31showed signs of alcoholic fermentation. The five most actively fermenting isolates were all identified as Saccharomyces cerevisiae. In brewing trials, all wild strains exhibited slower fermentation rates and produced approximately 80% of the alcohol yield achieved by the control. HPLC analysis revealed residual maltose concentrations of 0.5-1% in wild yeast fermentations, indicating reduced maltose assimilation capacity relative to the commercial strain. These results demonstrate the successful isolation of five wild S.cerevisiae strains from an urban natural environment in Kagoshima City. However, their inferior fermentation performance and incomplete maltose utilization suggest that further improvement is required prior to practical application. Adaptive mutation strategies targeting fermentative metabolism are expected to enhance the fermentation capacity of these strains, and their subsequent application in brewing holds promise for developing craft beers with a distinctive regional character through the novel perspective of indigenous yeast utilization.