Cold-active acid pectinolytic system from psychrotolerant Bacillus: Color extraction from red grape skin

Abstract

Cold-active enzymes are potentially relevant to food processing and, among them, pectinases belong to the most important enzymes in the fruit juice and wine industry. Bacillus sp. CH15 from grape berries was screened for the production of cold-active acidic pectinolytic enzymes. Taxonomic studies and 16S rDNA analysis revealed that the isolate was closely related to the Bacillus subtilis group. Maximum pectinolytic activity under acidic conditions (pH 5.0) and at low temperature (20°C) was obtained after 24 hr of incubation in medium containing citrus pectin as sole carbon source (0.305 U/mL). Polymethylgalacturonase activity was the predominant pectinase under the given assay conditions, whereas highest levels of pectate lyase activity were found at 60°C. At 5 and 10°C, the enzymatic system maintained 15 and 30% of the maximum activity, respectively. This is the first report on a pectinolytic enzyme system produced by a Bacillus strain and active at 20°C and pH 3.6, conditions similar to those in winemaking. According to classical and CIELab color parameters of short macerations with red grape skins at low temperature, the bacterial pectinolytic system produced a rapid color extraction and the macerates exhibited better chromatic characteristics than those obtained with commercial pectinases or after natural extraction. Total anthocyanin contents of the macerates with Bacillus enzyme system and after natural extraction were significantly different, whereas relative individual pigment quantities did not show any significant difference between the two treatments. In conclusion, Bacillus sp. CH15 could be used as a microbial source of cold-active acidic pectinases in red winemaking.