Reducing Cooling Costs for Sustainable Food Biomanufacturing With Thermotolerant Cupriavidus necator H16 Mutant.
Abstract
Autotrophic CO2 conversion to Single Cell Protein (SCP) using H2 and O2 is gaining commercial traction for food and feed production. Cupriavidus necator H16 is a key chassis organism for this "knallgas" fermentation, but industrial operation is typically constrained to ~30°C due to poor autotrophic growth at higher temperatures. Autotrophic growth at 37°C would enable the use of low-cost cooling water instead of chilled water, offering substantial reduction in cooling expenses. Here, we characterised a spontaneous C. necator mutant that conferred 37°C-thermotolerance when grown autotrophically, and compared its performance to the wild type. In batch cultures at 30°C, both strains showed comparable growth. At 37°C, only the spontaneous mutant grew autotrophically, albeit with a lower maximum growth rate than at 30°C. In chemostat cultivations no clear phycological differences could be resolved within the experimental uncertainty relative to the wild type at 30°C, in terms of PHB production, CO2 uptake at 37°C, and proteinogenic amino acid composition. Techno-economic modelling of a 160 kt a-1 SCP process indicated that operation at 37°C can reduce cooling utility costs up to 75%, saving ~US$ 0.98 per kg SCP (20%-50% of the production costs). Operating at 37°C with thermotolerant strains could subsequently decrease production costs substantially, making CO2-derived SCP production more economically viable at scale.