Biotechnological Approaches to Generate Biogenic Solvents and Energy Carriers from Renewable Resources

Abstract

Background: Current threats connected to the ongoing depletion of fossil resources and elevated levels of greenhouse gases accelerating climate change and global warming provoke a renaissance of biotechnological production of various organic bulk chemicals, which, particularly during the second half of the 20th century, were almost exclusively produced from fossil resources via chemosynthetic processes. Scope: Besides the manufacture of bioethanol, a product obtained by microbial fermentation, biogenic production of solvents and energy carriers like acetone, isopropanol, 2,3-butanediol, or 1-butanol, hence, processes known since the beginning of the last century, experiences now a substantial revival. Summary of new synthesis and conclusions reached in the review: The review illustrates how to produce these products by resorting to fossil raw materials instead of petrochemical production processes, and how this can be accomplished by the cultivation of anaerobic organisms, namely facultatively anaerobic yeasts and bacteria (production of ethanol or 2,3-butanediol), and strictly anaerobic Clostridia (1-butanol, acetone, or isopropanol) on renewable resources. Moreover, novel methods for producing biodiesel-like methyl-esters of aerobically produced bacterial polyhydroxyalkanoate biopolyester building blocks combine the synthesis of microbial biopolyesters from wastewater with the progress of innovative renewable energy carriers. The biochemical background, the current state of research and development, and the status of industrialization of these processes are reviewed. Conclusion: Challenges to make these bioprocesses, based on inexpensive renewable resources, competitive with or even superior to petrochemical production routes in terms of sustainability, scalability, and economic feasibility still exist: however, they can be overcome by the concerted action of various scientific disciplines.

Mixotrophic Syngas Conversion Enables the Production of meso-2,3-butanediol with Clostridium autoethanogenum

“…The aforementioned strictly anaerobic bacteria produce acetate, ethanol, and 2,3-butanediol, whereas C. carboxidivorans has the additional ability to produce butyrate, 1-butanol, hexanoate, and 1-hexanol. However, the concentrations of the C4-C6 products remain low, and the production of acids is not particularly favorable [22][23][24]. C. autoethanogenum, being an extensively studied and sequenced acetogen, is already employed for the industrial production of ethanol from steel-mill off-gases [10,25,26].…”