Valorization of faba bean peels for fungal tannase production and its application in coffee tannin removal.

This study describes the optimization of the production conditions of tannase on unutilized food waste, green bean peels, using the central composite of the response surface methodology. It also focuses on applying purified tannase to reduce tannins in coffee. The proposed design recommended a temperature of 29.07 °C, pH of 6.74, a tannin level of 6.76%, and 3.31% bean peels for maximum tannase production (313.40 U/g/min) by solid-state fermentation. This waste can be used as a sustainable and low-cost substrate for tannase enhancement by ≈5 folds. Applying purified tannase in instant coffee beverage resulted in a ≈ 23% reduction in tannins and a ≈ 16% increase in reducing sugars, with no significant changes in caffeine and phenolic compound contents. Tannase had a detrimental effect on the volume and stability of the coffee foam. This study will pave the way for tannase industrial production and its promising use in low-bitter coffee production.