The growing global population has led to a continuous increase in food demand, leading to an increase in the demand for protein for use in animal feed. In particular, China is facing a serious shortage of protein sources.

Despite being the world leader in pig production and aquaculture for many years, China remains heavily dependent on imported soybeans for animal feed, with annual imports of around 100 million tons and a dependence ratio exceeding 80%.

Therefore, developing methods to produce high-quality proteins quickly and efficiently is of great importance. And the most promising solution lies in synthetic biology.

There are several routes to bio-protein synthesis. The simplest is to convert by-products from the food and agricultural industries, such as corn steep liquor, distillers' grains, and rice straw, into higher value protein products through microbial transformation.

However, the supply and quality of these by-products are unstable, making industrial production difficult.

Another notable approach involving industrial fermentation using energy-producing chemicals is the use of methanol, which is cheaply derived from coal.

This is what scientists from the Tianjin Institute of Industrial Biotechnology of the Chinese Academy of Sciences (CAS), led by Professor Wu Xin, are researching.

“Coal, with global reserves of about 107 trillion tons, can be converted into methanol through coal gasification. Methanol mixes well with water, is more efficient in fermentation than gas, and does not require specialized fermentation equipment,” Professor Wu wrote in an article published in the China Science Bulletin.

His team has now developed a technology to produce proteins that is cheaper than traditional protein biosynthesis. The findings were published in the peer-reviewed international journal Biotechnology for Biofuels and Bioproducts on November 17, 2023.

“Research on synthesizing cell proteins from methanol began in the 1980s, focusing mainly on strain selection and process optimization. However, due to high costs, methanol-synthesized protein products cannot compete with soy protein and have not been produced on a large scale,” Professor Wu introduced in the article.

To address the problem, his team collected more than 20,000 yeast samples from vineyards, forests, and wetlands across China. From those samples, they identified strains that were able to efficiently use different sugars and alcohols as carbon sources, including the yeast strain Pichia pastoris.

Then, by knocking out specific genes in a wild strain of Pichia pastoris, they created a yeast with methanol tolerance and significantly enhanced metabolic efficiency. This technique greatly advanced the goal of converting methanol into protein.

“The researchers achieved dry cell weight and crude protein content of 120 g/liter and 67.2%, respectively, with their modified Pichia pastoris. And the methanol-to-protein conversion efficiency reached 92% of the theoretical value,” the CAS report said.

The high conversion rate makes this method of protein production very economically attractive.

“It does not require arable land, is not affected by seasons and climate, and is thousands of times more efficient than traditional fermentation methods. Moreover, the protein content of the microorganisms ranges from 40 to 85 percent, which is significantly higher than that of natural plants,” Professor Wu said in the paper.

These proteins are also rich in amino acids, vitamins, inorganic salts, fats and carbohydrates, allowing them to partially replace fishmeal, soybean, meat and skim milk powder in a variety of applications.

The team has begun industrial-scale research deployments, producing thousands of tons of methanol protein for animal feed. The specific partner was not disclosed.

Microbial proteins are highly nutritious and free of the allergens found in soy proteins, making them an excellent source of protein. However, there are only a few products on the market today.

The US company KnipBio has used genetically modified strains to produce KnipBio Meal, a high-quality feed protein comparable to fishmeal, from methanol. The product has received safety approval from the US Food and Drug Administration (FDA).

Hua Yu (Source: SCMP)