Aquaculture is the most efficient and fastest growing source of animal protein for humans but its continued sustainability is of grave concern. The continued reliance on fishmeal to support the growth of aquaculture is not an option anymore as many of the world’s fisheries are maximally exploited or in decline. Alternative protein sources to substitute for fishmeal have been developed, and current options primarily include those derived from plants.
The use of these plant-based proteins has reduced the amount of fishmeal required for aquaculture feed blends. For example, fish-in: fish-out ratios for salmon have been reduced from ~3.5-4:1 to a current ~1:1. Soy is the most common terrestrial plant protein used in aquafeeds, but anti-nutritional compounds and palatability to fish does not make it an ideal total replacement.
Furthermore, diseases can occur when using alternate proteins (e.g. gastroenteritis in salmon) as a direct result of sub-optimal feeding regimes. These difficulties add additional stresses and costs to the food supply chain.
KnipBio is advancing a single cell protein (SCP) technology with the target of developing sustainable solutions for animal nutrition. This SCP does not only provide a high content of protein, but it is also a source of essential amino acids and high value biomolecules like carotenoids. In nature, the KnipBio microbe is a ubiquitous leaf symbiont with the capability of creating single cell protein and other biomolecules of interest using commercially available, non-food based feedstocks.
With the availability of genetic tools, biotechnology uniquely offers a powerful means to rapidly advance specific desirable traits to support aquaculture’s growth potential. Just recently, KnipBio converted upon a bio-informatic prediction, resulting in a meaningful level of taurine produced for the first time in just a few months. Tailored applications, with rapid iteration, is representative of how technologies can lead to aquaculture’s next line of products, simultaneously avoiding chemically synthesized alternatives.
An alternative source of protein that has been developed previously with some success is SCP, or the protein-rich biomass collected from microbial processes. Today, it is very common to blend the spent yeast cells from corn ethanol fermentations with dried distiller’s grains and solubles (DDGS) used as animal feed. Algae, which are also an SCP, is grown commercially in ponds or bioreactors and often used in the manufacture of food and cosmetic ingredients, oils and nutritional supplements. Algal protein is comparable to conventional plant protein in many ways including nitrogen content and other nutritional factors. To date, its wide scale use has been limited by higher production costs and technical challenges. Other approaches to SCP production include harvesting from the residuals of wastewater treatment facilities’ clarifying ponds or dedicated manufacturing processes.
The last strategy holds the greatest potential for “smart proteins”, or advanced biotechnologies specifically customizable to solve specific nutritional challenges.
As fishmeal is systematically removed or reduced in diets, additional key nutrients beyond protein can also get diluted as a consequence. Nearly all protein alternatives to fishmeal have some inherent nutritional limitations, but these can potentially be overcome by adding ingredients back exogenously. Taurine (2-aminoethanesulfonic acid) is an amino acid found in a wide range of organisms, from birds, mammals, fish, plants, fungi and bacteria. Taurine is critical in many basic cellular processes, including osmoregulation, membrane stabilization, and antioxidation.
In addition, taurine participates in a variety of more complex physiological functions, such as bile conjugation, protein folding and calcium signaling. Taurine can be detected at high levels in a variety of fish species, and has been suggested as conditionally essential for many carnivorous fish species. From trout to snakehead, its supplementation has been shown to increase growth rate. Furthermore, it appears that its inclusion can complement the additional reduction of fishmeal in the feedstock, a critical objective for achieving a more sustainable form of aquaculture.
The prospect of a combined protein + taurine ingredient demonstrates the powerful potential to maximize nutritional solutions and the versatility of this approach. The application of this technology may be especially useful during the larval stages of fish or in crustacean diets, which can sit in the water longer than other feeds leading to losses due to dissipation. Chemically synthesized taurine is highly crystalline, particularly susceptible to leaching and can be less biologically available. Enriching rotifers with taurine is an effective solution, but an uneconomical one, as live feeds tend to be more expensive.
An alternative strategy is to encapsulate taurine in microparticles, such as lipid-walled capsules. Plant-based production systems could achieve this objective by employing the cell membrane as a natural lipid-capsule but this approach is imperfect as direct feeding with plant cells suffers from the anti-nutritional factors found in plant-based feeds mentioned above. Therefore, there exists a need for an aquaculture feed that protects taurine from dissolving in water, while avoiding solutions involving plant-based biosynthesis or live feeds.
Additional benefits to this bioprocess include the modularity of the KnipBio “brewery” for scale-up, which employs readily available fermentation equipment. The productivity of an advanced microbial manufacturing facility has the potential to produce >100-fold more protein per acre compared to soy, without the seasonality or other undue influences from climate change (e.g. droughts, floods).
These plants can be built in modular fashion and located nearly anywhere in the world as to be closer to markets they serve.
Deriving protein from non-food sources, plus the thermodynamic conservation gains from being lower on the food chain, represents significant resource efficiencies. The inputs of a fermentation process are carefully monitored leading to a consistent, clean source of protein in an era where environmental pollutants and traceability are a concern.
Ultimately, to meet the projected doubling of the aquaculture industry by 2030 that will grow in concert with the human population, new and innovative sources of protein are needed.
Those that can incorporate advanced biotechnologies like the one described here will be uniquely advantaged in both performance and resource constraints. SCP technologies have the potential to make meaningful contributions as a source of high quality protein, stabilize rising input costs and address the overharvesting of pelagic fisheries towards the reduction of fishmeal ultimately leading to a healthier, more sustainable food supply chain around the world.
This article was originally published in International Aquafeed - January 2017, p. 20-22.