Biodiesel fuel production by Aspergillus niger whole-cell biocatalyst in optimized medium

Methanolysis of sunflower oil catalyzed by immobilized Aspergillus niger mycelium was studied in a packed-bed reactor. The optimal cultivation parameters for A. niger were determined using full factorial and steepest ascent experimental designs. Sunflower oil, yeast extract and soybean meal were selected as the best carbon and nitrogen sources and were used in the subsequent experiments. Intracellular lipase activity and cell mass concentration were respectively 3.2 and 2.4 times greater and cultivation period decreased by 24 h compared with the initial medium. The optimum values of these most significant parameters were as follows: sunflower oil (13.2 g/L), yeast extract (6.2 g/L), soybean meal (7.4 g/L) and incubation period (72 h) at 30 °C. With A. niger biocatalyst grown in optimized conditions, the biodiesel fuel yield reached 23.1% after sixth pass of recycled reaction mixture through the reactor.