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The global demand for high-quality, protein-rich foods will continue to increase as the global population grows, along with income levels. Aquaculture is poised to help fulfill some of this demand, and is thus the fastest growing animal protein industry. A key challenge for it, though, is sourcing a sustainable, renewable protein ingredient. Single cell protein (SCP) products, protein meals based on microbial or algal biomass, have the potential to fulfill this need. Here, we review potential sources of SCP strains and their respective production processes, highlight recent advances on identification of new SCP strains and feedstocks, and, finally, review new feeding trial data on important aquaculture species, specifically Atlantic salmon, rainbow trout, and whiteleg shrimp.

A two-step combined system consisting of heterogeneous catalysis followed by dark fermentation was investigated for the production of biohydrogen. Cellulose in the aqueous phase was hydrolysed in an autoclave reactor with ZrO2 catalysts modulated by three different promoters: sulfate, fluoride, and phosphate. The water-soluble fractions (WSFs) resulting from the catalytic cellulose hydrolysis were then submitted to dark fermentation without any additional treatment. The dark fermentation step tested three different microorganisms – Enterobacter spH1, Citrobacter freundii H3 and Ruminococcus albus DMS20455 – for their ability to produce H2 from cellulose, glucose and the liquid product derived from cellulose hydrolysis. The two enteric bacteria (C. freundii H3 and Enterobacter spH1) effectively fermented the WSFs to produce H2 and other organic compounds as metabolites. For the WSFs derived from cellulose hydrolysis with ZrO2-P and ZrO2-S catalysts, the values for Enterobacter spH1 were 1.40 and 1.09 mol H2/mol hexose, respectively.