Hydrothermal Treatment of Coffee Residues for the Production of Pectinases by Paecilomyces Formosus

Lignocellulosic residues represent a low cost, high quality, and abundantly available alternative carbon sources that offer potential solutions to challenges linked to the growing demand for sustainability. In this study, the potential for the production of holocellulolytic enzymes induced by Paecilomyces formosus with agro-industrial coffee residues as substrates was evaluated. Enzymatic screening of eight strains revealed three major producers of pectinases (strains 3RET13, 3RE14, and 3RE21). For accurate molecular identification, sequence analysis was performed using the internal transcribed spacer regions 1 and 2 of nuclear ribosomal DNA, calmodulin, and beta-tubulin gene regions as DNA barcode markers. Response surface analysis was employed to determine the most appropriate pretreatment and cultivation conditions for the induction of pectinase, mannanase, xylanase, and endoglucanase enzyme activities. Different factors related to pretreatment (biomass concentration, exposure time, and temperature) and cultivation (pH, agitation, temperature, and nitrogen supplementation) were evaluated. Pectinase profiles were described for P. formosus strain 3RE21. A low-severity treatment with a lower biomass concentration (140 ?, 6 min, 1%) and milder cultivation conditions (20 ?, 87 rpm, pH 4.0, with no nitrogen supplementation) was considered optimal for the production of pectinases due to the high and rapid induction of these enzymes by the resulting liquor, with 2.11 UI/ml enzymatic activity, 11% reduction in total lignin content and 71% solubilization of the cellulosic and hemicellulosic portion observed with these conditions. The use of low-severity pre-treatments is widely used due to the financial and temporal investment of industries, as the compounds of interest are quickly and easily extracted from biomass as they are less exposed to the aggressive conditions of pre-treatments.

Automated summary

This study evaluated the potential of using agro-industrial coffee residues as substrates to induce the production of holocellulolytic enzymes by Paecilomyces formosus. The appropriate pretreatment and cultivation conditions for enzyme activity induction were determined using response surface analysis. Low-severity pretreatment and milder cultivation conditions were found to be optimal for pectinase production.