Solid-State Fermentation of Green Tea Residues as Substrates for Tannase Production by Aspergillus niger TBG 28A: Optimization of the Culture Conditions

Abstract

Tea (Camellia sinensis) is an evergreen shrub that is recognized worldwide for its functional properties. The current global production of green tea is approximately 5.3 million tons per year. Green tea processing has severely affected the generation of agro-industrial waste. One strategy for reducing waste accumulation is the revalorization of agro-industrial wastes via solid-state fermentation (SSF). The aim of this study was to valorize green tea processing residues to produce tannase under SSF using an endemic strain from Western Ghats, Aspergillus niger TBG 28A. SSF was performed in Erlenmeyer flasks with spent green tea leaves inoculated with spores of A. niger TBG 28A. Bioprocess optimization was carried out by employing the Box–Benkhen experimental design, achieving a high enzymatic yield of 246.82 (U/g). The present study shows the complexity of the degradation of tannins and the different patterns of expression of fungal tannase obtained from A. niger TBG 28 A. The enzyme was further purified to obtain a fold purification of 16.35% and a molecular mass of 150 kDa. Producing tannase with a novel strain of A. niger TBG 28A is an interesting strategy to revalorize green tea waste.