Negative H2S character and flocculation as yeast strain markers for inoculum recovery

Carlos Alberto França Ribeiro,Jorge Horii

doi:10.1590/s0103-90162004000300009

Carlos Alberto França Ribeiro, Jorge Horii

Open Access

https://doi.org/10.1590/s0103-90162004000300009

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Abstract

Routine identification of yeast behavior is essential to measure the control of the alcohol production process and to maintain product quality standards. This work utilized the non-hydrogen sulfide production and flocculation traits as characteristic strain markers for the evaluation of cell recycling during the alcoholic fermentation process for production of sugarcane alcohol. This study evaluated the behavior of a recombinant yeast bank made by protoplast fusion, for strain screening purposes; strain fermentative kinetics in comparison to commercial baker yeast; viability and recovery of the selected strain on differential media, after five consecutive fermentation batches; and the recovery of the selected strain from fermentation with mixed strain cultures. The strain selected for the H2S negative character kept its viability during successive recyclings, with contamination levels not detected by the method of analysis. It also presented a kinetic behavior similar to that of baker yeast, either in single or mixed culture fermentations, opening new possibilities for further work on quality control of cell recycling in the alcoholic fermentation process.

Highlights

Yeast is an important microorganism in the field of applied microbiology, and precise methodologies have been developed to study the growing relationships between yeast for various areas of research and development, technology and health
Microorganisms - This study evaluated 12 recombinant yeast populations obtained from protoplast fusions between auxotrophic mutants derived from a non-hydrogen sulfide producing strain (IZ 987), and the flocculant strain (ABXR 11B), stored as Yeast extract peptone dextrose agar (YEPDA) slant cultures covered with mineral oil and stored at 5°C (Martins et al, 1999)
Thirteen strains isolated by Martins et al (1999) with the desired traits and stored on YEPDA slant cultures at 5°C, and a strain isolated from a commercial baker yeast, were evaluated

Summary

Introduction

Yeast is an important microorganism in the field of applied microbiology, and precise methodologies have been developed to study the growing relationships between yeast for various areas of research and development, technology and health. Yeast acts as an agent for production as well as for the breakdown of products. Routine identification of yeast behavior is essential to measure the quality control of the alcohol production process and to maintain product quality standards. Standard industrial procedures routinely use among 80 to 100 morphologic and physiologic tests and the identification methods must be fast and inexpensive (Török & King Jr., 1991). Easier techniques have been developed for the identification of yeast, such as serologic testing (Campbell, 1971; 1972) and fatty acid chromatographic profiling (Oosthuizen et al, 1987). The most acceptable methods are the taxonomy handbooks by Barnett et al (1983), based upon physiological tests, and by Kreger-van Rij (1984), which describes species morphology without differentiating yeast strains within the same species

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