Overcome the Bottleneck of Reliable Depurine Technology by an Enzymatic Processing and Strive to Achieve the Strategic Goal of Replacing China's Meat Gap with Yeast Protein

攻克生物酶法脱嘌呤技术瓶颈

力争实现中国肉类缺口由酵母蛋白替代的战略目标

Abstract: Relying on the integrated innovation of industrial biotechnology talents, the establishment of efficient enzymatic depurine (denucleic acid) production process, that is, only nucleic acid removal, while avoiding the enzymatic degradation of protein components, the preparation of food safety grade yeast protein products, applied in the field of alternative protein manufacturing, to meet the needs of China's meat market gap. At the same time, professionals in the fields of food manufacturing, nutrition, flavor and other fields are requested to enter, carry out further research and division of labor to improve the technical parameters of yeast protein in water retention, oil philicity, flavor and other characteristics, truly bring yeast replacement protein foods to the table of the public, and strive to achieve the strategic goal of replacing Chine’s meat gap by yeast protein.

1. The development of alternative proteins is of great significance  

Food protein is one of the most important nutrient for human beings, with the functions of constituting and repairing human organs and tissues, transporting various substances, maintaining various physiological functions and providing energy. China's population has exceeded 1.4 billion, the per capita annual consumption of meat has reached 60 kg, and the total annual domestic demand for meat has reached 80 million - 100 million tons. The availability of existing proteins is highly dependent on cropping and animal husbandry, with livestock providing nearly 65% of the protein. More than 100 million tons/year of soybeans is imported to China, about 20% of the processed product is soybean oil, 80% of the processed product is soybean meal, which is the main raw material for livestock and poultry feed.

However, there is a greater awareness of the need for protein replacement based on the meat gap caused by population growth, the environmental hazards of animal husbandry, and the risk of chronic diseases associated with meat products. Alternative proteins will dramatically improve food systems, mitigate the impact of food production on climate change, dramatically improve public health, and offer tremendous opportunities for innovation, investment and economic growth.

In response to the growing protein food shortage, the necessity of constructing sustainable high-quality protein substitutes is very clear.  At present, the replacement proteins are mainly plant-based proteins and microbial proteins. Plant-based proteins are primarily based on soy protein. In recent years, China's annual import of soybeans has reached and will exceed 100 million tons. Due to the limitation of land area, the potential risk of genetically modified products and the safety risk of high concentrations of flavonoids in soy protein (high concentrations of soy isoflavones have adverse effects on the reproductive system of both men and women).  China mainly relies on soy protein to develop alternative protein main products, which is not feasible. The alternative protein produced by microbial fermentation has gradually attracted the attention of the government and the scientific and technological circles with the advantages of low resource consumption, high efficiency, environmental protection and sustainability, and comprehensive nutrition, and is in a priority position for development.

2.Feasibility and technological breakthroughs in developing food grade yeast single cell protein

Based on safety, nutrition, and sustainability of industrial production, microbial single-cell proteins have been considered as the ultimate alternative protein, especially Saccharomyces cerevisiae single-cell proteins. 

Yeast protein is an all-natural, nearly perfect balanced nutrition food, is an ideal source of nutrition. Yeast has the characteristics of "three low and four excellent", low fat, low sugar, low cholesterol, containing high-quality protein (all essential amino acids), complete B vitamins, 14 rare mineral elements and high-quality dietary fiber.Yeast proteins are high-quality proteins with high bioavailability and can be used as novel alternative proteins for food-grade applications.

Saccharomyces cerevisiae has been used to make human food for more than a thousand years. Saccharomyces cerevisiae is rich in a variety of nutrients, such as protein content of 45% ~ 60%, rich in essential amino acids, including lysine 5% ~ 7%, sulfur amino acids 2% ~ 3%. And rich in B vitamins, such as B1, B2, B6, B12, pantothenic acid, folic acid, niacin, polysaccharides, etc. More unique is that the B vitamins in yeast are in the form of phosphate esters, which are more absorbed and utilized by the human body. However, due to the high nucleic acid content and low cell wall digestibility of Saccharomyces cerevisiae, the further development of food-grade yeast protein products has been restricted.

Overcoming the limitations of high purine (nucleic acid) content and high cost, improving the functional properties and sensory acceptability of yeast proteins will greatly promote their market application.

The high content of yeast protein nucleic acid can cause gout, metabolic imbalance, urinary stone positive and other diseases. The methods of industrial production to remove Nucleic acid methods are mainly alkali method and enzymatic method. The alkaline method leads to the loss of protein nutrients and the production of toxic product lysine alanine. Enzymatic methods cannot be further promoted due to the high cost of enzyme preparations used.

Duringthe past 10 years, the production technology has undergone fundamental changes, and the continuous progress and improvement of molecular biology technology represented by genetic engineering and protein engineering has entered a new period of development of the enzyme preparation industry. The application of biotechnology integration research results to complete the industrial, low-cost production of highly vigorous nuclease systems , applied to  removal nucleic acid production process of yeast protein, so that the yeast protein extract RNA content from 6-8% to 0.6-0.8%, completely reached the food grade safety level. After efficient removal of nucleic acids, it makes the physical recovery of yeast protein easier, and the recovery rate is increased by 5-10%, further improving the economy of yeast protein.

The second challenge to yeast protein becoming the ultimate alternative protein is the low utilization rate of cell wall digestion. The cell wall of Saccharomyces cerevisiae accounts for 20%~30% of the dry weight of the cell, and the glycan component composed of β-glucan and mannan accounts for about 77% of the yeast cell wall component. Such glycans show strong anti-digestion and are not easy to be digested and absorbed by the human body for use.

Using modern food technology, yeast cell wall polysaccharides are prepared into resistant starch-like and applied to low-carbon diets. Current studies have shown that resistant starch plays a powerful role in promoting health, including improving insulin sensitivity, lowering blood sugar levels,  losing weight by reducing appetite, and improving digestive system function. There are 140 million diabetic patients and almost 700 million pre-diabetic patients in China. The introduction of this type of resistant starch-like into the field of low-carbon diet can greatly reduce the intake of starchy foods without changing the normal diet.

3.Research and development of yeast single-cell proteins and related products

Microbial proteins mainly include yeast proteins, bacterial proteins, macrofungal proteins, etc. Yeast protein contains all essential amino acids, is a full valent protein, rich in nutrition and mature fermentation process, no allergenic components, suitable for a wide range of people.

According to the composition of yeast cells, the following related products are produced to further improve the economy of yeast protein series: 1. Food grade yeast protein products, protein content can be controlled at 50-80%. 2. Cell wall polysaccharide products, β-glucose and mannan. 3. Food-grade yeast extract rich in various coenzyme components and B vitamins, especially rich in vitamin B12, which generally does not exist in plant foods and can be applied to functional foods. Due to their low salt, cholesterol and fat content, functional foods can be used in the prevention and treatment of cardiovascular diseases, hypertension diseases and blood sugar control. 4. In the production process of yeast single-cell protein, the production of 1 million tons of products, while about 30,000 tons of purine and pyrimidine heterocyclic compounds can be obtained, which is of great significance for the development of new engineering materials.

4.Yeast single-cell protein is sustainable and sustainable, shouldering the mission of agricultural carbon reduction

Developing yeast protein as the ultimate alternative protein is a four-step process. In the first step, molasses and starch sugar fermentation is used to produce yeast protein. In the second step, yeast protein is produced by fermentation of potatoes, sweet potatoes and tapioca starch sugar of high-yield crops. The third step is to produce yeast protein from waste brewer's yeast, alcoholic yeast, and agricultural and forestry waste and catering waste. The fourth step is to use non-food biomass, that is, crops and plant straw as fermentation raw materials to produce yeast protein. Through the bioconversion and utilization of renewable resources, the source of fermentation raw materials is expanded, and the problems of food shortage and environmental pollution are solved under the condition of ecological balance.

5.Achieve the strategic goal of replacing China's meat gap with yeast protein

Yeast protein production cycle is short, high efficiency, does not seize land resources, is not affected by seasons, climate, more environmentally friendly, can significantly improve protein production efficiency and reduce carbon dioxide emissions. The most important advantage is that it can achieve industrial production, and its efficient production efficiency is that the gap of meat protein in China can be replaced by yeast protein to achieve. 1, 200 x 200M³ fermenter can produce 1 million tons of high-quality yeast protein. 2, the equivalent of 5 million cows and 1 billion chickens produced protein products, reducing 6 million tons of CO2 emissions. 3, equivalent to the protein provided by 20,000 beef cattle (according to a cow 500 kg, about 250 kg of meat, about 50 kg of pure protein). 4, the global beef production is about 60 million tons, pure protein 12 million tons of pure protein. The 2400 x 200M³ fermenter produces protein equivalent to global beef production. The annual output of yeast protein in a 380 x 200M³ fermenter is equivalent to the protein content of beef production in China.

Yeast single cell protein production cost analysis: At the initial stage, molasses or starch sugar is used as the main production raw material, according to the production experience of the yeast industry, starch sugar accounts for about 60% of the production cost. Combined with 3 tons of starch sugar to produce 1 ton of yeast protein, it is estimated that the production cost of yeast protein per ton is 15000-20000 million yuan. In theory, the protein content of yeast  protein accounts for about 50%, and the production cost of yeast pure protein (100% purity) is 30,000-40,000 million yuan/ton.

Yeast Pure Protein vs. Pork & Beef Pure Protein Price Comparison: The pork (Market Price 20RMB/kg, protein content is calculated at 15%) pure protein is 130,000 RMB/ton; Beef (market price 70 yuan/kg, protein content calculated at 20%) pure protein 350,000 yuan/ton. Compared with the price of pork and beef, from the perspective of pure protein production cost, yeast protein is only 0.27 times that of pork and 0.1 times that of beef.

Economic comparison of yeast protein and plant-based soybean meal: Due to the nutritional balance of soybean meal protein amino acids, the high concentration of phytoestrogen soy isoflavones and the high content of anti-nutritional factors affecting the human gastrointestinal tract, soy protein cannot be directly and indefinitely applied to the food industry. Soybean meal protein is used in the aquaculture industry, indirectly obtaining pork, chicken, beef protein to meet the demand of the meat market. Scientific studies have shown that 81.7% of protein is lost in the transition from plant protein to animal protein. According to this calculation, 10 tons of soybean meal (soybean meal protein content is about 45%, soybean meal price is about 4000 yuan / ton) to obtain 1 ton of animal protein, and the consumption of soybean meal reaches 40,000 yuan. Accordingly, yeast protein economy still has a price advantage.

Yeast protein is a natural, almost perfect balanced nutritional food, which can make alternative protein meat and replace the current demand of about 10 million tons in the meat market. As an ideal substitute for livestock meat products, alternative protein meat is the main alternative product to solve the shortage of traditional animal husbandry, and it is of great strategic significance to China's food security problem and livestock product supply system adjustment.

6. Summary

Due to the rapid increase in population, the limitation of land resources, and environmental and climatic pressures, traditional food protein production methods can no longer meet the future needs of human life. Industrial-scale, low-cost, sustainable protein production requires innovation and development. The use of microbial proteins to replace animal protein is an inevitable direction for the food and biological industries.

Utilizing the most advanced biotechnology to break the efficient depurination (nucleic acid) bottleneck technology of yeast protein, industrialized production of food safety grade nutritional yeast protein products. Applied in the field of alternative protein, gradually meeting the demand for tens of millions of tons of alternative meat in the market.