Efficient ammonia production from food by-products by engineered Escherichia coli

Abstract

Ammonia is used as a fertilizer for agriculture, chemical raw material, and carrier for transporting hydrogen, and with economic development, the demand for ammonia has increased. The Haber-Bosch process, which is the main method for producing ammonia, can produce ammonia with high efficiency. However, since it consumes a large amount of fossil energy, it is necessary to develop an alternative method for producing ammonia with less environmental impact. Ammonia production from food by-products is an appealing production process owing to unused resource usage, including waste, and mild reaction conditions. However, when food by-products and biomass are used as feedstocks, impurities often reduce productivity. Using metabolic profiling, glucose was identified as a potential inhibitor of ammonia production from impure food by-products. We constructed the recombinant Escherichia coli, in which glucose uptake was reduced by ptsG gene disruption and amino acid catabolism was promoted by glnA gene disruption. Ammonia production efficiency from okara, a food by-product, was improved in this strain; 35.4 mM ammonia was produced (47% yield). This study might provide a strategy for efficient ammonia production from food by-products.

Sustainable Biological Ammonia Production towards a Carbon-Free Society

“…Therefore, by knocking out the glucose transporter ptsG and deleting phosphoenolpyruvate, the phosphotransferase system, which transports major sugars such as glucose in E. coli, and the strain succeeded to produce ammonia of about 73% yield from sugar-containing amino acid medium. Additionally, ammonia production from pretreated soybean residues also succeeded for the first time with a conversion efficiency of about 47% and a high concentration of about 35 mM (Figure 2b) [106]. In these studies, ammonia was produced intracellularly, which led to a tradeoff between microbial growth and ammonia production.…”

“…Biomass, such as food waste, is also promising for producing various substances and as animal feed because it contains fixed nitrogen in various forms, such as proteins and nucleic acids [100][101][102][103][104][105][106]. For example, food waste can be used as organic fertiliser by digesting it with anaerobic bacteria [11].…”

“…Several attempts to produce ammonia from organic molecules containing nitrogen have been made (Table 1) [100,[102][103][104][105][106]. For example, there is a study using Bacillus subtilis [102].…”

“…However, the above two studies were mainly experiments using amino acid-containing medium, and actual food waste was not used. Oriented toward the use of actual food waste, ammonia production from six media and four types of food waste was investigated using E. coli [106]. Furthermore, the correlation between the concentration of substances, such as amino acids, sugars, and organic acids, in the media and ammonia production was analysed by metabolic profiling, and it was found that glucose should inhibit ammonia production.…”

“…Metabolic engineering Amino acids-based medium [102] Escherichia coli Metabolic engineering Amino acids-based medium [112] Escherichia coli Metabolic engineering Amino acids-based medium and soybean residue [106] Saccharomyces cerevisiae Cell surface engineering Glutamine solution and soybean residue [104] Saccharomyces cerevisiae Cell surface engineering Amino acids solution and soybean residue [105] Several attempts have been made to produce ammonia extracellularly. In some studies, yeast cell surface engineering systems have been used to avoid intracellular ammonia assimilation and toxicity [105,113,114].…”