Valorisation of side streams from wheat milling and confectionery industries for consolidated production and extraction of microbial lipids

• A consolidated process for production and extraction of microbial lipids is proposed.
• Filter-sterilized crude hydrolysates were advantageous for biomass and oil production.
• Carbon to FAN ratios of crude hydrolysates were optimised in fed-batch cultures.
• Fungal crude enzymes were utilised for Rhodosporidium toruloides cell disruption.

Crude enzymes produced via solid state fermentation (SSF) using wheat milling by-products have been employed for both fermentation media production using flour-rich waste (FRW) streams and lysis of Rhodosporidium toruloides yeast cells. Filter sterilization of crude hydrolysates was more beneficial than heat sterilization regarding yeast growth and microbial oil production. The initial carbon to free amino nitrogen ratio of crude hydrolysates was optimised (80.2 g/g) in fed-batch cultures of R. toruloides leading to a total dry weight of 61.2 g/L with microbial oil content of 61.8% (w/w). Employing a feeding strategy where the glucose concentration was maintained in the range of 12.2–17.6 g/L led to the highest productivity (0.32 g/L · h). The crude enzymes produced by SSF were utilised for yeast cell treatment leading to simultaneous release of around 80% of total lipids in the broth and production of a hydrolysate suitable as yeast extract replacement.