The search for new β-glucosidase from yeast sources is important to improve the quality of wines. In this work, an S. pararoseus yeast strain has shown to be capable to produce a β-glucosidase with suitable combination of properties for functionality in wines and with potential to increase the concentration of free aroma compounds, showing good prospects for an industrial application.
Nineteen fungi and seven yeast strains were isolated from sugarcane bagasse piles
from an alcohol plant located at Brazilian Cerrado and identified up to species level
on the basis of the gene sequencing of 5.8S-ITS and 26S ribosomal DNA regions. Four
species were identified: Kluyveromyces marxianus,
Aspergillus niger, Aspergillus sydowii and Aspergillus
fumigatus, and the isolates were screened for the production of key
enzymes in the saccharification of lignocellulosic material. Among them, three
strains were selected as good producers of hemicellulolitic enzymes: A. niger
(SBCM3), A. sydowii (SBCM7) and A. fumigatus
(SBC4). The best β-xylosidase producer was A. niger
SBCM3 strain. This crude enzyme presented optimal activity at pH 3.5 and 55 °C (141
U/g). For β-glucosidase and xylanase the best producer was A.
fumigatus SBC4 strain, whose enzymes presented maximum activity at 60 °C
and pH 3.5 (54 U/g) and 4.0 (573 U/g), respectively. All these crude enzymes
presented stability around pH 3.0–8.0 and up to 60 °C, which can be very useful in
industrial processes that work at high temperatures and low pHs. These enzymes also
exhibited moderate tolerance to ethanol and the sugars glucose and xylose. These
similar characteristics among these fungal crude enzymes suggest that they can be
used synergistically in cocktails in future studies of biomass conversion with
potential application in several biotechnological sectors.
Microbial β-glucosidases have been used for the enhancement of wine aroma. Nevertheless, few enzymes are active in the conditions of winemaking. In this work, the production of a β-glucosidase by an Aureobasidium pullulans strain (Ap-β-gl) isolated from grape ecosystems was evaluated. The maximum enzymatic synthesis using submerged fermentation was after 96 h of growth in complex media containing 20 g/L of cellobiose as the sole carbon source. The crude enzyme (Ap-β-gl) showed optimal pH at 5.5 and two peaks of optimum temperature (at 45 and 70 °C). It showed a wide range of pH stability, stability at low temperatures, and tolerance to ethanol, showing suitable characteristics for winemaking conditions. The hydrolysis of glycosidic terpenes by Ap-β-gl was studied, and its ability to efficiently release free terpenols was demonstrated by gas chromatography/mass spectrometry. The enzymatic treatment notably increased the amount of monoterpenes, showing good prospects for its potential application for the development of aroma in wines.
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