The single-cell protein feed that does not require sunshine and a lot of land is here!
Sprint for the fourth quarter
The treatment of biogas slurry with high concentration of ammonia nitrogen is the bottleneck for the development of biogas and bio-natural gas industries in my country.
But under the "magic" of scientists, this problem is being solved.
Recently, Chengdu Institute of Biology, Chinese Academy of Sciences announced that it has made new progress in the research project of producing single-cell protein feed from biogas slurry——
The utilization and technical route of using biogas liquid ammonia nitrogen to produce microbial single-cell protein feed can convert biogas slurry with high concentration of ammonia nitrogen into microbial single-cell protein feed for breeding.
While avoiding secondary pollution, it realizes the high-value biological conversion and utilization of biogas liquid ammonia nitrogen.
This research result is of particular practical significance in the context of "carbon neutrality".
Talk about meaning /
Construction of "Ammonia Nitrogen-Protein Nitrogen" One-Step Conversion Nitrogen Cycle
Extend the industrial chain and value chain of biogas and biogas
Researcher Li Dong from the Biomass Energy Project Group of Chengdu Institute of Biology, Chinese Academy of Sciences is the project leader.
He mentioned that in recent years, anaerobic digestion technology, also known as biogas fermentation technology, has been widely used in the treatment of livestock and poultry farming manure, kitchen waste, industrial organic wastewater and residues, and is an internationally recognized resource utilization of organic waste. Mainstream technology.
However, while producing clean energy (biogas or biogas), a large amount of high ammonia nitrogen biogas slurry will be produced.
At present, the utilization and treatment methods of biogas slurry are mainly used as fertilizer and used as waste water for treatment and discharge.
Li Dong mentioned that although biogas slurry is used as a liquid fertilizer to return to the field is a good choice, it requires a lot of land for planting and is greatly affected by the climate.
The most important thing is that due to the imbalance of planting and breeding in my country and the limited land surrounding the biogas project, it is difficult to completely absorb the biogas slurry. When the application of biogas slurry exceeds the carrying capacity of the land, it is a pollutant that will pollute the water body. It is easy to cause secondary pollution.
In addition, the efficiency of biogas liquid fertilizer is low, and the transportation cost is high. Therefore, it is more difficult to use it as fertilizer in the field.
In order to avoid secondary pollution, it is a last resort to treat biogas slurry as wastewater for biological denitrification treatment and discharge up to the standard.
Li Dong introduced that the current treatment of high-ammonia-nitrogen biogas liquor uses traditional physicochemical methods, biological methods and other sewage treatment processes. These processes are all through the "nitrification-denitrification" biological process to convert ammonia nitrogen into nitrogen and discharge it into the atmosphere.
In fact, the ammonia nitrogen in the biogas slurry mainly comes from the protein nitrogen in the organic waste. The protein nitrogen comes from the fertilizer nitrogen used in the planting stage, and the fertilizer nitrogen is the nitrogen compound obtained by converting the nitrogen in the air by the synthetic ammonia plant spending a lot of natural gas energy. .
"In nature, ammonia nitrogen is a precious nitrogen resource obtained through biological nitrogen fixation. If we use the method of'nitrification-denitrification' to treat the biogas slurry, the ammonia nitrogen is converted into nitrogen and discharged into the atmosphere. Uneconomical and even useless redundant nitrogen cycles."
Under this realistic background, Li Dong proposed: "If we use feed to build a very economical and effective short-flow nitrogen cycle for the one-step conversion of'ammonia nitrogen-protein nitrogen', it will not only avoid secondary pollution, but also realize resource utilization. Utilize and extend the industrial chain and value chain of biogas and bio-natural gas."
Talk about progress /
Pilot test will be carried out in the near future
Large-scale applications are expected to land in the future
In order to realize the high-value biological conversion and utilization of liquid biogas ammonia nitrogen, Li Dong proposed in 2016 the utilization and technical paths of biogas liquid ammonia nitrogen to produce single-cell protein feed.
Researcher Li Dong's team first isolated two oxidizing bacteria with autotrophic, heterotrophic and mixed nutrition ability to produce single-cell protein from soybean rhizosphere soil, fish pond wastewater, and biogas slurry, namely Paracoccus denitrificans. Y5 and Paracoccus variabilis Paracoccus.versutus D6.
These two hydrogen oxidizing bacteria have unique metabolic characteristics. They can synthesize single-cell protein heterotrophically from organic carbon sources such as glucose and ammonia nitrogen. At the same time, they can use carbon dioxide as an inorganic carbon source and autotrophic synthesis of ammonia nitrogen under the condition of providing reducing power hydrogen. Single cell protein.
The single-cell protein content of strains Y5 and D6 is 67.34%～73.73% of the dry cell weight, which is much higher than the protein content of soybean, and the protein of Y5 has a richer amino acid composition than soybean protein.
"This research provides more options for the high-value utilization of biogas slurry." Li Dong said that when the concentration of chemical oxygen demand in biogas slurry is high, heterotrophic culture can be carried out to use ammonia nitrogen to produce single-cell protein; When the COD concentration is low, autotrophic culture can be carried out, using biogas or the carbon dioxide and ammonia nitrogen generated from the exhaust gas to produce single-cell protein to help achieve the goal of "carbon neutrality".
However, the cell biomass (dry cell weight) concentration of hydrogen oxidizing bacteria is low.
In order to further increase the dry weight concentration of bacteria, the team of researcher Li Dong selected two strains from more than 10 strains of yeast that can tolerate chicken manure biogas slurry and efficiently utilize the ammonia nitrogen of biogas slurry to produce single-cell protein. They are honey yeast (Nectaromyces rattu). ) And Galactomycescandidum (Galactomycescandidum).
Through experiments, it was found that under the same conditions, through the secondary fermentation of honey yeast, the total dry cell weight (CDW) can reach 12.58g/L, and the protein content is 35.96%; through the secondary fermentation of Geotrichum candidum, the total dry cell weight (CDW) can be reached. ) 9.24g/L, protein content 39.39%.
In addition, the project team also found through research that the sulfur in organic waste is converted to hydrogen sulfide during anaerobic digestion and is lost with biogas. Therefore, the two yeast single-cell proteins lack cysteine and methionine. Acid and other sulfur-containing amino acids.
By adding sulfate, the project team not only promoted the synthesis of sulfur-containing amino acids, but also significantly increased the protein content by promoting the synthesis of glutamic acid and glutamine. The total amino acid content was increased from 38.6g/100g to 53.2g/100g.
Compared with plant-derived protein feeds, the microbial single-cell protein obtained by processing high-concentration ammonia nitrogen biogas slurry through this biotechnology has a faster synthesis rate, does not require sunlight and a large amount of land, and can use waste carbon sources (such as brewing yellow water). , Molasses, starch wastewater, etc.), the production cost is also lower.
Microbial single-cell protein feed can be used for breeding, such as aquaculture.
Li Dong revealed that at present, the project is in the small-scale test stage, and the pilot-scale test will be carried out in the near future, and it is expected to be applied on a large scale in the future.
Chengdu Commercial Daily-Red Star News reporter Peng Xiangping