Utilization of waste activated bleaching earth containing palm oil in riboflavin production by Ashbya gossypii

Waste activated bleaching earth (ABE) discharged by an oil refinery plant, which contained 40% palm oil, was used for riboflavin production by a culture of the filamentous fungus Ashbya gossypii. When 188 g/L waste ABE containing 75 g/L palm oil was added to the culture, 80% of the palm oil was consumed after 4 d, and the riboflavin concentration reached 2.1 g/L after 10 d of culture. This concentration was almost 1.5 times higher than for cultures grown on pure palm oil, in which case only 68% of the palm oil was consumed. Before the culture was initiated, the surface of the waste ABE was smooth and resembled clay that was covered with palm oil. After the culture, the oil content decreased to 8%. The black color of waste ABE gradually faded and turned yellow, with the ABE finally forming a yellow powder. Eighty percent of the riboflavin produced during the culture period was transferred to oil‐depleted waste ABE and the waste‐oil‐depleted ABE had 14 mg of riboflavin/g of oil‐depleted waste ABE. The waste ABE containing waste palm oil was suitable for use as a raw material for the production of value‐added riboflavin. Thus, this research might provide a good model for the reuse of waste resources containing vegetable oil.