Chocolate industry side streams as a valuable feedstock for microbial long-chain dicarboxylic acid production

• Published in: Biochemical engineering journal 2021-03, Vol.167, p.107888, Article 107888
• Main Authors: Bauwelinck, Jordy, Caluwé, Michel, Wijnants, Marc, Wittner, Nikolett, Broos, Waut, Dries, Jan, Akkermans, Veerle, Tavernier, Serge, Cornet, Iris
• Format: Article
• Language: English
• Subjects: Bioconversion; Bioprocess modelling; Candida tropicalis; Long-chain dicarboxylic acids; Wastewater valorisation
• ISSN: 1369-703X; 1873-295X
• DOI: 10.1016/j.bej.2020.107888

•Residual liquid chocolate can be valorised by conversion of its fat content to dicarboxylic acids (DCA).•Dissolved air flotation (DAF) sludge shows no toxic effects on yeast growth up to 80 v%.•Fats from DAF sludge can be converted to long chain dicarboxylic acids by C. tropicalis.•‘Chocolate water’ could be used at high solids concentration without toxicity and with reasonable DCA yield. Two high-fat containing side streams from the chocolate industry were evaluated as an alternative renewable substrate for biochemical long-chain dicarboxylic acid (DCA) production by Candida tropicalis. Cleaning water from liquid chocolate transport and dissolved air flotation (DAF) sludge from the wastewater treatment plant contained 29 and 18 m% fat respectively. The addition of up to 100 g.L−1 of the ‘chocolate water’ and 80 % (v/v) of DAF sludge had no negative effects on both growth and DCA production. In a fed-batch reactor, a DCA concentration of 5.8 g.L−1 was obtained after 120 h and 47.5 % of the consumed fats were converted to DCA upon glucose addition when using chocolate water. Using DAF sludge, a DCA concentration of 4.9 g.L−1 was obtained after 72 h, equalling 37.5 % of the consumed fats. This research shows the potential of the researched side streams as a substrate for DCA production.