Citric acid production by Aspergillus niger van. Tieghem MTCC 281 using waste apple pomace as a substrate

A solid state fermentation process was tried for the production of citric acid from apple pomace left after juice extraction using Aspergillus niger van. Tieghem MTCC 281 spores as inoculum (36.8 × 104 spores/100 g of pomace). The yield of citric acid was optimized by varying the amount of methanol (1–5% v/w), temperature (25–35°C) and time of incubation (1–7 days) for fermentation process. Optimum yield of citric acid (4.6 g/100 g of pomace) was recorded with 4% (v/w) methanol after 5 days of incubation at 30°C.