Production of Gallic Acid Under Solid-State Fermentation by Utilizing Waste from Food Processing Industries

Gallic acid (3,4,5-trihydroxybenzoic acid) is an industrially important organic acid that is found in plants as secondary metabolite. It possesses wide range of applications in healthcare, food and pharmaceutical industry, in manufacturing inks, paints, dyes and also in cinematography. The annual consumption of gallic acid in Pakistan is 8000 tons which is mainly met by importing this item from developed countries. This study was planned to assess the potential of various tannin rich bio-wastes [e.g., peels (banana, pomegranate, apple, and mango) and seeds (black plum, mango, apple, and tamarind)] from fruit processing industries to produce gallic acid by using Aspergillus niger via solid state fermentation. Different physical and chemical parameters were optimized to get the optimum yield of gallic acid. Among all bio-wastes, black plum seed powder gave highest yield of gallic acid i.e. 13.31 mg/g of substrate; the parameters being: substrate water ratio of 1:3, 72 h of incubation period, 2 mL of inoculum, pH 5 and temperature of 30 °C. Carbon source supplementation i.e., glucose increased the synthesis of gallic acid to 14.5 mg/g of substrate while addition of nitrogen sources had negative effect. Extraction of gallic acid was done by using Soxhlet extraction apparatus while FTIR was used for characterization. The solid state fermentation protocol for the production of gallic acid from tannin rich biowastes has been developed and proved to be cost-effective method. The results presented can be optimized further on large scale for industrial production of gallic acid.