Sustainable fish feed innovation: Microbial protein from soybean wastewater
New research has shown that repurposing wastewater from soybean processing for milk and meat alternatives may provide a solution.
In a recently published paper, as highlighted by Anthropocene, Singapore University-based researchers documented their evaluation of microbial community-based single cell protein (SCP) derived from soybean processing wastewater as a partial substitute for fishmeal protein in juvenile Asian seabass (Lates calcarifer).
Food processing wastewaters
SCP grown on food processing wastewaters (FPWW) holds promise as a sustainable source of protein in animal feed, say the Singaporean team.
"FPWW possess attractive features for SCP production, including a continuous global production of process water rich in dissolved carbon (C), nitrogen (N), and phosphorus (P) compounds. These wastewaters are also considered free of pathogens, heavy metals, and other harmful contaminants. FPWW can support microbial growth in bioreactors, from which cells can be recovered and dried to create products suitable for animal feed ingredients. This process avoids the cost of treating such wastewaters and represents an important step toward a circular bioeconomy."
The study
Wastewater from a soybean processing company in Singapore was supplied for use in small bioreactors and incubated it for several days at 30°C to encourage microbial growth. The protein-enriched bacteria was then harvested from the sludge, dried, combined with water, and processed it into a mash suitable for fish feed.
The SCP was composed of beneficial genera Acidipropionibacterium and Propioniciclava, known for their probiotic properties and valuable metabolite production, reported the authors.
Feeding trial
During a 24-day feeding trial, fish were fed either a control fishmeal diet or an experimental diet with 50% fishmeal replaced by the microbial SCP.
Both diets met the nutritional needs of juvenile Asian seabass, except for lysine, said the team.
Results showed no significant differences in growth performance, feed conversion ratio (FCR), specific growth rate (SGR), and survival between the control and experimental groups after 24 days.
The experimental group had less variability in terms of weight gain and FCR than the control group.
“This preliminary trial study showed that 50% of fishmeal protein might be replaced with microbial community-based SCP produced from soybean processing wastewater without affecting Asian seabass growth or survival, and that an SCP replacement diet may also lead to less variable fish growth than a traditional diet containing only fishmeal as protein source," noted the authors.
Future studies should consider longer growth periods and higher fishmeal replacement levels, as well as additional aquaculture species and other types of FPWW, they continued.
“Overall, we demonstrated that microbial community-based SCP has potential as an alternative value-added ingredient for aquaculture feed, which can help in the transition to a circular bioeconomy."
