Engineering the Dark Food Chain

Abstract

Meeting global food needs in the face of climate change and resource limitation requires innovative approaches to food production. Here, we explore incorporation of new dark food chains into human food systems, drawing inspiration from natural ecosystems, the history of single cell protein, and opportunities for new food production through wastewater treatment, microbial protein production, and aquaculture. The envisioned dark food chains rely upon chemoautotrophy in lieu of photosynthesis, with primary production based upon assimilation of CH4 and CO2 by methane- and hydrogen-oxidizing bacteria. The stoichiometry, kinetics, and thermodynamics of these bacteria are evaluated, and opportunities for recycling of carbon, nitrogen, and water are explored. Because these processes do not require light delivery, high volumetric productivities are possible; because they are exothermic, heat is available for downstream protein processing; because the feedstock gases are cheap, existing pipeline infrastructure could facilitate low-cost energy-efficient delivery in urban environments. Potential life-cycle benefits include: a protein alternative to fishmeal; partial decoupling of animal feed from human food; climate change mitigation due to decreased land use for agriculture; efficient local cycling of carbon and nutrients that offsets the need for energy-intensive fertilizers; and production of high value products, such as the prebiotic polyhydroxybutyrate.

Microbes and Climate Change: a Research Prospectus for the Future

“…Aboveground methanotrophic bioreactors can potentially convert recovered methane into valuable products, such as single-cell protein or bioplastics, while also generating methanotrophic biomass that can be incorporated into landfill cover soil. Challenges to the design and operation of such bioreactors are mass transfer limitations due to the low solubility of methane and oxygen, safe management of methane/oxygen mixtures, and provisions for heat management ( 24 ).…”

A rheological approach to identify efficient biopolymer producing bacteria

“…For example, in the case of Bacillus subtilis , a change of the overall membrane potential is not required for chemotaxis. Thus, despite the highly exothermic nature of the aerobic methanotrophic growth process (El Abbadi & Criddle, 2019), we cannot consider that the consumption of methane during the growth of the bacteria directly affects their locomotion performance. On the other hand, the pieces of evidence from this study suggest that the efficiency of bacterial motion could be related to biopolymer production.…”

Photovoltaic-driven microbial protein production can use land and sunlight more efficiently than conventional crops

“…After extensive trials, the European Union approved bacterial SCP feeds (grown on natural gas) in 1995 as nutritional support for the diets of pigs, veal calves, and salmon (at levels of up to 8%, 8%, and 33% of their total feed, respectively) (47). Moreover, due to the rapid growth of the aquaculture sector and concomitant concerns of overfishing for fishmeal, there is an increasing commercial interest in microbial proteins destined for aquaculture (15,54). Although the projected PV-SCP production prices are currently higher than soymeal or fishmeal, SCP could become more economically viable if the externalized costs linked to pollution, GHG, and ecosystem disruptions caused by extensive soy cultivation and fishing were reflected in prices by policy incentives (45).…”

“…Yet the technology shows promise, as previous reports demonstrate that SCP uses water and nitrogen resources far more efficiently than crops (54,58). Modern agriculture relies on large inputs of chemical nitrogen fertilizers to support crop productivity due to low N uptake by plants (≈50%) (59).…”

“…In contrast, inreactor SCP production can be tuned to use all the supplied reactive N, thereby performing conversion of inorganic N to edible protein without losses (59). Furthermore, plants and animals use ≈100 and ≈10,000 times more water than SCP (54,60). This makes SCP an attractive option for regions facing both water and food security risks.…”