Characterization of pectinase activity for enology from yeasts occurring in Argentine Bonarda grape

Pectinolytic enzymes are greatly important in winemaking due to their ability to degrade pectic polymers from grape, contributing to enhance process efficiency and wine quality. This study aimed to analyze the occurrence of pectinolytic yeasts during spontaneous fermentation of Argentine Bonarda grape, to select yeasts that produce extracellular pectinases and to characterize their pectinolytic activity under wine-like conditions. Isolated yeasts were grouped using PCR-DGGE and identified by partial sequencing of 26S rRNA gene. Isolates comprised 7 genera, with Aureobasidium pullulans as the most predominant pectinolytic species, followed by Rhodotorula dairenensis and Cryptococcus saitoi. No pectinolytic activity was detected among ascomycetous yeasts isolated on grapes and during fermentation, suggesting a low occurrence of pectinolytic yeast species in wine fermentation ecosystem. This is the first study reporting R. dairenensis and Cr. saitoi species with pectinolytic activity. R. dairenensis GM-15 produced pectinases that proved to be highly active at grape pH, at 12 °C, and under ethanol and SO₂ concentrations usually found in vinifications (pectinase activity around 1.1 U/mL). This strain also produced cellulase activity at 12 °C and pH 3.5, but did not produce β-glucosidase activity under these conditions. The strain showed encouraging enological properties for its potential use in low-temperature winemaking.

Avaliação da produção de melanina por espécies de Cryptococcus em quatro diferentes meios de cultura / Evaluation of melanin production by Cryptococcus species in four different culture media

A capacidade de Cryptococcus spp produzir melanina em meios contendo compostos fenólicos é amplamente utilizada na identificação destas espécies no laboratório. O objetivo do presente trabalho foi comparar a produção desse pigmento em quatro meios de cultura por Cryptococcus sp. Foram testadas 16 cepas de Cryptococcus neoformans, 17 de Cryptococcus albidus, 13 de Cryptococcus laurentii, e 2 de Cryptococcus uniguttulatus nos meios: ágar batata e cenoura, ágar alpiste, ágar semente de girassol e ágar L-dopa. A produção de melanina foi avaliada com base na pigmentação das colônias, e demonstrada em 5 dias de incubação por 93,8 por cento das cepas de Cryptococcus neoformans nos meios ágar batata e cenoura, ágar semente de girassol e ágar L-dopa. Dos isolados de Cryptococcus albidus, 29,4 por cento produziram o pigmento em ágar batata e cenoura e L-dopa, 11,8 por cento em ágar alpiste, e 36 por cento em ágar girassol. De Cryptococcus laurentii, 53,8 por cento produziram em batata e cenoura e em semente de girassol, 61,5 por cento em L-dopa, 84,6 por cento em ágar alpiste. Somente uma cepa de Cryptococcus uniguttulatus produziu fracamente o pigmento em ágar batata e cenoura.

The capacity of Cryptococcus spp to produce melanin in media containing phenol compounds is widely used for identifying these species in the laboratory. The aim of the present study was to compare the production of this pigment by Cryptococcus spp. in four culture media. Sixteen strains of Cryptococcus neoformans, 17 of Cryptococcus albidus, 13 of Cryptococcus laurentii and two of Cryptococcus uniguttulatus were tested in the following media: potato-carrot agar, Niger seed agar, sunflower seed agar and L-dopa agar. The melanin production was evaluated on the basis of colony pigmentation. Its production after five days of incubation was demonstrated by 93.8 percent of the strains of Cryptococcus neoformans in the media of potato-carrot agar, sunflower seed agar and L-dopa agar. From the isolates of Cryptococcus albidus, 29.4 percent produced the pigment in potato-carrot agar and L-dopa agar, 11.8 percent in Niger seed agar and 36 percent in sunflower seed agar. From Cryptococcus laurentii, 53.8 percent produced the pigment in potato-carrot agar and sunflower seed agar, 61.5 percent in L-dopa agar and 84.6 percent in Niger seed agar. Only one strain of Cryptococcus uniguttulatus presented slight production of the pigment, in potato-carrot agar.