Agriculture is crucial for supplying food and raw materials to society, however, limited arable land and escalating climate change pose significant challenges. Thus, meeting the growing demands is becoming increasingly difficult. The use of low-carbon compounds derived from the CO₂ reduction for customizing sugar derivatives marks an achievement. However, the variety of available low-carbon raw materials remains meager, the range of synthesized products is restricted, and the sugar yields remain relatively low.  

In this study, the researchers proposed an approach for producing glucose through the microbial transformation of C_1–3 products, namely methanol, ethanol, and isopropanol, originating from inorganic CO₂ fixation processes.  

Initially, the researchers expanded the range of carbon sources for microbial cell factories by studying yeast's utilization of various low-carbon compounds. Apart from ethanol, Saccharomyces cerevisiae can use ethylene glycol (C₂), isopropanol (C₃), propanoic acid (C₃), and glycerol to support cell growth and glucose production. Through an engineered Pichia pastoris system, methanol (C₁) was efficiently converted into glucose, achieving yields of 1.08 g/L in shake flasks and 13.41 g/L in fermenters.  

Moreover, the researchers utilized ethanol, methanol, isopropanol, and glycerol as carbon sources, diversifying carbohydrates, including xylose, xylitol, myo-inositol, glucosamine, sucrose, and starch. In particular, yields of myo-inositol and glucosamine in shake flasks were noteworthy at 228.71 mg/L and 69.99 mg/L, respectively. Sucrose production quantified at 1.17 g/L in shake flasks and 25.41 g/L in fermenters. Remarkably, the microbial production of starch—a ubiquitous compound in our lives—achieved 341.59 mg/L in shake flasks 

Furthermore, the researchers introduced an effective method for producing high-carbon compounds using low-carbon sources. In the glucose study, production nearly doubled through the adjustment of glucose inhibition impacts.  

Experimental results showed that engineered yeast achieved a protein content of approximately 50% of cell dry weight. This indicated that the proposed technology is not only adept at efficiently producing carbohydrate food compounds from low-carbon materials but also yields single-cell protein as a beneficial coproduct.  

"Our work provides directions for microbial sugar-derived foods and chemicals production from renewable reduced CO₂-based feedstocks," said Prof. YU.