Isolation and selection of pectinase-synthesising bacteria from soil and coffee husk for application in coffee fermentation

Abstract

Pectinase is a group of enzymes that hydrolyse pectin, a polysaccharide found in plant cell walls, into low molecular compounds such as galacturonic acid, galactose, arabinose, methanol, etc. Pectinase can be used in foods as it does not affect human health. This study was conducted to isolate and select bacterial strains capable of pectinase biosynthesis and determine the factors affecting pectinase activity of bacterial strains as a basis for applied research to remove pectin during fermentation to produce coffee. 32 bacterial strains were isolated from samples of coffee soil and dried coffee pods collected in the Tay Nguyen and Quang Tri, of which the 4 strains with the highest pectinase activity were DA2.7; DA3.1; DA4.1 and VC1.1. Selected bacterial strains were identified to species based on 16S rRNA gene sequences, specifically: strains DA2.7, DA3.1 are homologous to species Calidifontibacillus erzurumensis; strain DA4.1 is homologous to the species Bacillus stercoris; strain VC1.1 is homologous to the species Bacillus subtilis. The suitable fermentation conditions for pectinase-producing strain VC1.1 is pH 5.0 at 50ºC for 48 hours. Pectinase is applied in coffee fermentation to obtain a product with a soluble solids content of 6.10°Brix and caffeine of 0.6 mg/100 mg.