Milling byproducts are an economically viable substrate for butanol production using clostridial ABE fermentation

Birgit Lewandowski,Johanna C Panitz,Wolfgang Liebl,Claudia Held,Wolfgang H Schwarz,Nils Thieme,Vladimir Zverlov

doi:10.1007/s00253-020-10882-8

Abstract

Butanol is a platform chemical that is utilized in a wide range of industrial products and is considered a suitable replacement or additive to liquid fuels. So far, it is mainly produced through petrochemical routes. Alternative production routes, for example through biorefinery, are under investigation but are currently not at a market competitive level. Possible alternatives, such as acetone-butanol-ethanol (ABE) fermentation by solventogenic clostridia are not market-ready to this day either, because of their low butanol titer and the high costs of feedstocks. Here, we analyzed wheat middlings and wheat red dog, two wheat milling byproducts available in large quantities, as substrates for clostridial ABE fermentation. We could identify ten strains that exhibited good butanol yields on wheat red dog. Two of the best ABE producing strains, Clostridium beijerinckii NCIMB 8052 and Clostridium diolis DSM 15410, were used to optimize a laboratory-scale fermentation process. In addition, enzymatic pretreatment of both milling byproducts significantly enhanced ABE production rates of the strains C. beijerinckii NCIMB 8052 and C. diolis DSM 15410. Finally, a profitability analysis was performed for small- to mid-scale ABE fermentation plants that utilize enzymatically pretreated wheat red dog as substrate. The estimations show that such a plant could be commercially successful.Key points• Wheat milling byproducts are suitable substrates for clostridial ABE fermentation.• Enzymatic pretreatment of wheat red dog and middlings increases ABE yield.• ABE fermentation plants using wheat red dog as substrate are economically viable.Graphical abstract

Highlights

The urgency to shift our current society and industry to more environmentally friendly alternatives has increased in recent years, as more and more studies showed that the resulting global warming will have detrimental effects on nature, human society, and health (Millington et al 2019; Sun et al 2019; Ahima 2020)
Identification of strains with high butanol yield on wheat milling byproducts The collection of bacterial strains from the Chair of Microbiology (TUM), which is composed of type strains as well as newly isolated wild strains, was screened for ABE fermenting clostridia strains that are suitable for consolidated bioprocessing of milling byproducts (Table 1)
A total of 30 strains were tested for ABE fermentation in Grundmedium YAF25 (GM) plus either 7.2% wheat red dog or 13% wheat middlings as carbon source

Summary

Introduction

The urgency to shift our current society and industry to more environmentally friendly alternatives has increased in recent years, as more and more studies showed that the resulting global warming will have detrimental effects on nature, human society, and health (Millington et al 2019; Sun et al 2019; Ahima 2020). Many possible avenues are explored to mitigate a global crisis, one of them being the replacement of petrochemical processes with sustainable biorefinery approaches to produce chemicals such as n-butanol. These processes have a reduced carbon dioxide emission compared with conventional production. Bio-butanol can be produced by several solventogenic clostridial species trough acetone-butanol-ethanol (ABE) fermentation (Lee et al 2008), which was already used on an industrial scale up to the 1960s (Zverlov et al 2006). Cheaper feedstocks need to be made available for a sustainable and economically profitable production of butanol

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