Abstract
Lignocellosic ethanol production is now at a stage where commercial or semi-commercial plants are coming online and, provided cost effective production can be achieved, lignocellulosic ethanol will become an important part of the world bio economy. However, challenges are still to be overcome throughout the process and particularly for the fermentation of the complex sugar mixtures resulting from the hydrolysis of hemicellulose. Here we describe the continuous fermentation of glucose, xylose and arabinose from non-detoxified pretreated wheat straw, birch, corn cob, sugar cane bagasse, cardboard, mixed bio waste, oil palm empty fruit bunch and frond, sugar cane syrup and sugar cane molasses using the anaerobic, thermophilic bacterium Thermoanaerobacter Pentocrobe 411. All fermentations resulted in close to maximum theoretical ethanol yields of 0.47–0.49 g/g (based on glucose, xylose, and arabinose), volumetric ethanol productivities of 1.2–2.7 g/L/h and a total sugar conversion of 90–99% including glucose, xylose and arabinose. The results solidify the potential of Thermoanaerobacter strains as candidates for lignocellulose bioconversion.
Highlights
As yeasts have been used for ethanol production for thousands of years they are considered to be the obvious candidate for lignocellulosic ethanol production
Thermoanaerobacter italicus Pentocrobe 411 was tested in continuous fermentations of different lignocellulosic substrates to investigate the limits to ethanol productivity, ethanol concentration and yield
The data presented here demonstrate that Thermoanaerobacter Pentocrobe 411 is capable of achieving high ethanol yields and productivities on a broad range of biomasses including wheat straw, birch, corn cob, sugar cane bagasse, oil palm empty fruit bunches and frond, mixed waste from food production and cardboard in high temperature continuous fermentation systems
Summary
As yeasts have been used for ethanol production for thousands of years they are considered to be the obvious candidate for lignocellulosic ethanol production. Lignocellulosic hydrolysates, create a completely different fermentation environment as they contain organic inhibitors, including acetic acid and phenolic lignin degradation products, and significant amounts of sugars that are not naturally fermented by industrial ethanol-producing yeasts. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Estibio ApS provided support in the form of salaries for authors [RLA, KMJ, and MJM], but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section
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