Coffee Husk: A Potential Agro-Industrial Residue for Bioprocess

Abstract

Agro-industrial processing always generates waste materials. Coffee is one of the largest commodities in the world, and its processing yields coffee husk as waste by-product. Its disposal without proper treatment can cause serious environmental problems. Coffee husk contains carbohydrates including fermentable sugars, polyphenols such as tannins, lipids. Various microorganisms including filamentous fungi are reported to grow on it despite the presence of antimicrobial compounds. Chemical nature of coffee husk makes it a suitable and inexpensive source for solid-state fermentation. Several studies have been reported on the application of coffee husk in bioprocess. It acts as a substrate as well as carbon source during fermentation. Production of various enzymes such as xylanases, cellulases, polygalacturonases, polyphenol oxidases, tannases in high titers can be achieved by fermentation using coffee husk as substrate. Apart from production of enzymes, bioconversion of coffee husk is also achieved during bioprocess which in turn favors sustainable utilization of waste products. Production of citric acid, gibberellic acid, gallic acid, polyhydroxyalkanoates (PHA), and bacterial cellulose is reported by fermentation using coffee husk as substrate. Mass production of microorganisms is another advantage of using coffee husk in bioprocess. It is excellent for the growth of various biocontrol agents such as Trichoderma sp. Besides economic production, prolonged shelf life of biocontrol agents multiplied on coffee husk makes it more attractive. Biopesticides such as Bacillus sphaericus and B. thuringiensis can also be produced by solid-state fermentation on coffee husk. The sustainable management of agro-industrial waste like coffee husk through bioprocess makes it as an attractive source of wealth.