Engineering alternative bacterial platforms for sustainable bioproduction

Modern biotechnology depends on a handful of well-characterised microbial species cultivated on sugar-derived feedstocks. Despite their success, these platforms face fundamental constraints: dependence on agricultural resources, vulnerability to contamination, and limited tolerance to unconventional process conditions. Alternative species with native capabilities for one-carbon assimilation, gas fermentation, saline cultivation, or growth at extreme conditions offer compelling solutions, yet their development potential remains largely untapped. Commonly labelled "non-model", these organisms differ enormously in technological maturity - a distinction critical for assessing feasibility, timelines, and risk. Here, we propose a four-tier engineering readiness framework and apply it to six representative platforms: Moorella thermoacetica, Sporomusa ovata, Xanthobacter sp. SoF1, Methylococcus capsulatus, Halomonas bluephagenesis, and Rhodococcus wratislaviensis. For each, we assess metabolic opportunity space, genetic toolkit development, industrial deployment, and key bottlenecks, illustrating a spectrum from promising wild isolates to tractable engineering platforms.