Fermentation Accelerates Development of Alternative Protein Industry

Alternative proteins produced by microbial fermentation contain no cholesterol, antibiotics , or growth hormones. In addition, the production cost of fermented proteins is lower, and they exhibit high biological efficacy. With the rapid growth of the global alternative protein industry, microbial fermentation alternative-derived proteins are rapidly growing in technology and scale, offering advantages such as resource efficiency, high efficiency, environmental sustainability, and comprehensive nutrition.

What are Alternative Proteins?

Animals have traditionally been considered the primary source of proteins, but this method is inefficient and cruel, involving long growth cycles and substantial resource and land consumption. Alternative proteins, distinct from traditional sources, significantly reduce environmental impact. Alternative proteins encompass plant proteins and food technology alternatives to animal or meat proteins, sourced from plants (grains, legumes, nuts, and seeds), algae (macro and microalgae), insects, microbial fermentation, and cell cultivation.

Fig. 2 Sustainable alternative protein sources. (Munialo, 2022)

Recently, synthetic biology has become a new research focus, with alternative proteins being a key application. As an interdisciplinary field, the rapid development of underlying technologies and applications, such as DNA synthesis and assembly techniques, has facilitated the rapid, efficient construction of complex genetic components. Biological computer-aided design and manufacturing tools have promoted the design of biological systems and processes. Synthetic biology enables the rapid, high-throughput construction, testing, and optimization of organisms to ultimately achieve efficient production of alternative proteins.

Alternative Protein Industry

Key factors determining the alternative protein industry include structural protein supply, policies, capital, alternative protein technology processes, market foundation, and consumers. Currently, alternative proteins surpass traditional products in terms of safety, nutritional adaptability, and price. Scientific research has validated the benefits of alternative proteins, leading companies worldwide to actively establish and expand infrastructure, transitioning toward more sustainable and innovative protein sources. The number of plant-based meat manufacturers has exceeded 100, and many fermentation companies have announced plans for new or expanded facilities. Governments globally increasingly recognize the importance and urgent need for developing alternative proteins, prioritizing the promotion of easily scalable plant-based protein products. With many new companies and brands entering the market, the alternative protein industry is maturing.

What is Fermented Protein?

Fermentation refers to the process of using the life activities of microorganisms under aerobic or anaerobic conditions to prepare microbial cells themselves or the direct metabolites or secondary metabolites. Fermentation has extensive applications in the food industry, biotechnology, and chemical industry.

In the process of replacing traditional protein sources, fermented proteins have significant advantages and potential. The production of fermented proteins relies on the rapid reproduction of specific microorganisms. In the final stages of fermentation, microbial cells are broken down to obtain concentrated proteins and isolates. Fermentation products can be directly used as the main components of food. With the support of biotechnology, the types and yields of proteins can be precisely controlled, with only a fraction of the energy and nutrients required by traditional methods. Importantly, all of this occurs in fermentation tanks, reducing dependence on land and minimizing environmental impact.

Fig. 2 Fermentation-derived proteins. (Linder, 2023)

Safety of Fermented Protein Applied in Food

Safety is the primary consideration for whether fermented protein can be used as a raw material in food production. Factors affecting the safety of fermented proteins include the safety of microbial production materials, RNA content in proteins, whether microorganisms themselves produce toxins, and potential allergens. The strains producing proteins cannot be pathogens, and they must not produce toxins. Residual heavy metal content in production materials must not exceed requirements. Microbial cultivation and product processing must be contamination-free, with no solvent residue or heat damage. The final product must be sterile, without live cells or solvent residue. Fermented protein products must undergo animal toxicity and carcinogenicity experiments, as well as human clinical trials, to determine human tolerance and acceptability before being used in food production.

Fermentation-Derived Microbial Protein

The adaptability of fermentation allows it to play a role in almost the entire field of alternative proteins, supporting plant-based and cell-culture methods. Microbial fermentation serves as a means of processing and functionalizing plant components, a major biomass source rich in proteins, and a flexible platform for producing various high-value components, driving the next generation of alternative protein products. Efforts in strain development and target selection will expand the capabilities of fermentation as a production platform and increase efficiency. Measures in bioprocess design and raw material optimization are expected to achieve greater sustainability benefits while reducing costs.

Microbial Protein Production

• Methylotrophic yeast protein

Methylotrophic yeasts include strains such as Pichia pastoris, Ogataea polymorpha, and Candida boidinii. These yeasts grow using methanol as a carbon source through the XuMP pathway. In methylotrophic yeast, methanol is first oxidized to formaldehyde by alcohol oxidase. Then, formaldehyde reacts with Xu5P to produce 3-phosphoglyceraldehyde and dihydroxyacetone phosphate, entering the sugar fermentation pathway for cell metabolism. The process of methylotrophic yeast cells using methanol to generate formaldehyde occurs in peroxisomes, reducing the toxicity of formaldehyde to cells and enhancing cell growth. Methanol is a clean and abundant energy source, and its utilization makes methylotrophic yeast advantageous for protein production. The efficiency of methanol utilization determines the economic viability of its protein production process.

• Chemoautotrophic microbial protein

Acetogenic bacteria are anaerobic chemoautotrophic bacteria that use CO or CO₂ as a carbon source and H2 as a reducing agent through the Wood-Ljungdahl pathway to produce fuel ethanol, microbial protein, and other high-value chemicals. The fermentation process of acetogenic bacteria and other chemoautotrophic bacteria is compatible with existing industrial fermentation technologies, making them ideal microbes for constructing single-carbon gas bioconversion cell factories.

• Photoautotrophic microbial protein

Microalgae are important photoautotrophic microorganisms that convert CO₂ into glyceronealdehyde-3-phosphate through the Calvin-Benson-Bassham cycle. Microalgae use chlorophyll to split H₂O into oxygen, ATP, and NADPH during the light reaction phase of photosynthesis. In the dark reaction phase, they use the ATP and NADPH generated in the light reaction to assimilate CO₂ into organic compounds for their own growth. Microalgae have a fast growth rate, with protein fractions reaching up to 70%, making them a significant source of single-cell protein. Microalgae protein contains abundant chlorophyll, vitamins, and unsaturated fatty acids (EPA and DHA ), with low nucleic acid content, showing potential for producing functional high-protein foods.

References

1. Munialo, C. D., et al., Extraction, characterisation and functional applications of sustainable alternative protein sources for future foods: A review, Future Foods, 2022, 6, 100152.
2. Linder, T., Fulfilling the Promises of Fermentation-Derived Foods, GEN Biotechnology, 2023, 2, 3.