Biotechnological application of yeasts in food science: Starter cultures, probiotics and enzyme production.

This review is an account of experiences of two research teams (from Italy to Spain); the leading idea is the following: yeasts represent valuable sources in food science and microbiology and are a kind of food factories, because of the potentiality of whole cells or for their produced compounds. This review covers three major areas: the first section addresses the role of yeasts as starter cultures with a special focus on wine. The second section is an update on probiotic yeasts. Finally, the focus of the last section is on enzymes produced by yeasts, with a short description of the removal of mycotoxin.

Optimization of a rapid method for studying the cellular location of beta-glucosidase activity in wine yeasts.

AIMS: To improve a method for determining beta-glucosidase activity and to apply it in yeasts isolated from wine ecosystems from "La Mancha" region and to know its cellular location. METHODS AND RESULTS: A total of 82 wine yeasts were identified (PCR/RFLP) and evaluated for their beta-glucosidase activity. First, they were qualitatively evaluated by growth on YNB cellobiose, the activity was quantified using different culture media, under aerobic and anaerobic conditions and cells after 24-72 h of growth. To study the location activity, five fractions were obtained (supernatant, whole cell, cell wall, cytosol and cell membrane). The enzymatic assays were optimized, being: growth in YP cellobiose for 72 h in aeration conditions and, after cell removing, enzyme analysis with 128 g l(-1) of cellobiose as substrate, for 30 min at 30 degrees C. The genus that displayed the greatest activity were Pichia, Hanseniaspora and Rhodotorula, and the activity was intracellular. CONCLUSIONS: The study showed that beta-glucosidase activity was induced by the carbon source and was aerobic dependent. The non-Saccharomyces species displayed the greatest activity, which was intracellular and strain-dependent. SIGNIFICANCE AND IMPACT OF THE STUDY: This study developed a reliable method for screening beta-glucosidase activity in yeasts isolated from wine ecosystems. This activity is very important in the release of monoterpenols from glycoside precursors for the enhancement of wine aromas.