A novel gas biotechnology

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Background: The projected growth of global population will place strains on the environment, natural resources and global food supply chain. Greenhouse gas emissions and plastic wastes have raised great concerns over the climate change and ocean pollution. Sustainable food supplies require more nutritional food and feed produced by using less land, water and resources. Our CO2-to-products technology platform presents a solution to the sustainability challenges by converting CO2, a major greenhouse gas emission, into environmentally friendly plastics and affordable nutritional proteins. Technology outline: In the novel process, CO2 in flue gas or other gas waste is directly absorbed and converted into single cell proteins by natural hydrogen-oxidizing microorganisms. The H2 and O2 gases used in the microbial CO2 fixation are generated from water electrolysis by using renewable powers such as solar, wind, hydro and geothermal electricity. Under the controlled conditions, the autotrophic microbes can also form polyhydroxybutyrate (PHB) as a carbon storage material. PHB is a natural thermoplastic that exhibits the material properties of polypropylene and completely decomposes into benign products (CO2, water) in the environment including marine waters. The core of the technology platform is a novel continuous flow gas fermentation bioreactor engineered for unique merits including: (1) no mixing of H2 and O2 gas for high operation safety, (2) no H2 waste discharge for high product yield (1.5-2 g /g H2), (3) direct use of CO2-rich gas waste for a low carbon cost, (4) significantly enhanced gas mass transfer rate (50-400% increase), and (5) high productivity of bioproducts (1-3 g L-1 h-1). The high productivity makes the industrial gas fermentation economically feasible. The microbial cells harvested from a reusable mineral solution contain a large amount of PHB (>60% w/w) and the rest protein-rich (65-75% w/w) cellular mass. A proprietary separation technology recovers PHB and protein hydrolysates of good digestibility. Supplemented with the protein hydrolysates, a heterotrophic microbial growth generates a very high yield (80-160% increase), which demonstrates the superior nutritional value of the oligopeptides and amino acids in the hydrolysates. Conclusion: The new CO2-to-products technology overperforms the conventional photosynthetic CO2 fixation by green plants and microalgae, because of its high energy efficiency, high productivity and low stains on resources. The technology could be applied in non-arable area, playing a great role in carbon circular economy. It is a sustainable alternative for agriculture, food and plastics industries. Work in plan: We will scale up the bioreactor capacity to 200 L and 1000 L in two steps to generate sufficient amounts of bioplastics and protein hydrolysates for products evaluation and marketing. The natural plastics will be used in a new design of food packaging that does not generate hazardous wastes after use. Feed trails will be conducted to confirm the nutritional performance of protein hydrolysates in feed for animals such as salmon, shrimp, pigs and pets. The consistent and successful trial results, in terms of growth, digestibility and gut health benefits, shall validate that the protein hydrolysate is a high-performance protein source. In addition, we will conduct a life cycle assessment (LCA) comparing the protein hydrolysates with conventional protein sources used in animal feed, such as soy protein concentrate and fish meal. The LCA study will account for all unit operations in our production process, from CO2, water and renewable powers to the end use in feed and food packaging. Thus far, the LCA results on natural plastics indicate that PHB has the lowest impact on climate change compared to conventional plastics, in terms of total energy consumption and total greenhouse gas (GHG) emissions per kg of plastics. Contact: Professor Dr. Jian Yu, University of Hawaii at Manoa, email: [email protected]