Effects of soybean curd wastewater on growth and DHA production in Aurantiochytrium sp.

Soybean curd wastewater (SCWW) is a by-product of the compression of protein coagulants performed during production of soybean curd (tofu). In this study, SCWW was used as a low-cost nutrient source for the cultivation of an Aurantiochytrium strain known to produce significant amounts of polyunsaturated fatty acids (PUFAs), such as docosahexaenoic acid (DHA). Instead of sterilization of the SCWW medium by heating (which promotes the Maillard reaction and production of hydroxymethylfurfural), the SCWW medium was sterilized using peracetic acid (PAA) followed by neutralization with a ferric ion solution. The growth of cells was similar in PAA-sterilized SCWW medium and sterile-filtered or autoclaved M7D20 medium that contained commercial components (glucose, yeast extract, and peptone). Surprisingly, cells grown in PAA-sterilized SCWW medium had more than 4-fold greater production of DHA than cells grown in autoclaved or filtered M7D20 medium.