Unlocking the genomic potential of aerobes and phototrophs for the production of nutritious and palatable microbial food without arable land or fossil fuels

Abstract

The increasing world population and living standards urgently necessitate the transition towards a sustainable food system. One solution is microbial protein, i.e. using microbial biomass as alternative protein source for human nutrition, particularly based on renewable electron and carbon sources that do not require arable land. Upcoming green electrification and carbon capture initiatives enable this, yielding new routes to H2, CO2 and CO2-derived compounds like methane, methanol, formic- and acetic acid. Aerobic hydrogenotrophs, methylotrophs, acetotrophs and microalgae are the usual suspects for nutritious and palatable biomass production on these compounds. Interestingly, these compounds are largely un(der)explored for purple non-sulfur bacteria, even though these microbes may be suitable for growing aerobically and phototrophically on these substrates. Currently, selecting the best strains, metabolisms and cultivation conditions for nutritious and palatable microbial food mainly starts from empirical growth experiments, and mostly does not stretch beyond bulk protein. We propose a more target-driven and efficient approach starting from the genome-embedded potential to tuning towards, for instance, essential amino- and fatty acids, vitamins, taste,... Genome-scale metabolic models combined with flux balance analysis will facilitate this, narrowing down experimental variations and enabling to get the most out of the 'best' combinations of strain and electron and carbon sources.

Fig. 1

Transition towards electron donors and carbon sources that are not relying on arable land or fossil fuels, enabled by ‘green’ electrification of the chemical industry based on water electrolysis and carbon capture and utilization approaches. These routes can generate several electron donors and/or carbon sources such as hydrogen gas (H₂), methane (CH₄), methanol (CH₃OH), formic acid (HCOOH), acetic acid (CH₃COOH) and carbon dioxide (CO₂), which are directed to the production of several major classes of chemotrophic and phototrophic microbes and metabolisms. A simplified technology readiness level (TRL), based on the Horizon 2020 work programme definitions, indicates the highest level of maturity of the microbial protein production technology. For commercial products (TRL 5‐9), examples of brand names are indicated, and for others, indicative scientific literature sources are given (TRL 1‐4). Copyright‐free images were sourced from Freepik.com.

Fig. 2

Proposed genome‐scale computational approach for targeted screening and nutritional quality steering. Grey boxes show the necessary steps in the route from computational prediction to downstream processing. Yellow boxes represent the variables of each step in the pipeline. The decreasing height of the green arrows depicts the number of variables (parameter values or options) to select in each step. Each step interacts with the key performance indicator. CAPEX, capital expenditure; OPEX, operational expenditure. This figure has been designed using resources from Freepik.com and flaticon.com.