Metabolic engineering of Thermoanaerobacterium AK17 for increased ethanol production in seaweed hydrolysate

Sustainably produced renewable biomass has the potential to replace fossil-based feedstocks, for generation of biobased fuels and chemicals of industrial interest, in biorefineries. In this context, seaweeds contain a large fraction of carbohydrates that are a promising source for enzymatic and/or m...

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Bibliographic Details
Published in:	Biotechnology for biofuels Vol. 16; no. 1; pp. 1 - 15
Main Authors:	Moenaert, Antoine, Bjornsdottir, Bryndís, Haraldsson, Einar Baldvin, Allahgholi, Leila, Zieri, Anna, Zangl, Isabella, SigurÃ°ardóttir, SigríÃ°ur, ürlygsson, Jóhann, Nordberg Karlsson, Eva, FriÃ°jónsson, Ãlafur H, HreggviÃ°sson, GuÃ°mundur Ãli
Format:	Journal Article
Language:	English
Published:	London BioMed Central Ltd 11-09-2023 BioMed Central BMC
Subjects:	Acetaldehyde Acetates Acetic acid Agricultural Sciences Alcohol Alcohol, Denatured Algae Anaerobic bacteria Annan lantbruksvetenskap Antibiotics Biofuel Biomass Biomass energy Biorefineries Biorefinery Carbohydrates Carbon Carbon sources Chemical Engineering Chemical Process Engineering Chemical properties Chemical Sciences Dextrose Engineering and Technology Enzymes Esters Ethanol Fermentation Förnyelsebar bioenergi Genes Genetic aspects Genetic engineering Glucose Hexoses Hydrolysates Industrial microorganisms Kemi Kemiska processer Kemiteknik Lactic acid Laminarin Lantbruksvetenskap och veterinärmedicin Lignocellulose Macroalgae Mannitol Marine algae Metabolic engineering Metabolism Methods Microbial enzymes Microbiological synthesis Microorganisms Natural Sciences Naturvetenskap Oligosaccharides Other Agricultural Sciences Physiological aspects Plasmids Production data Production processes Raw materials Refining Renewable Bioenergy Research Seaweed Seaweeds Substrates Teknik Thermoanaerobacterium Yeast Germany Iceland
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Summary:	Sustainably produced renewable biomass has the potential to replace fossil-based feedstocks, for generation of biobased fuels and chemicals of industrial interest, in biorefineries. In this context, seaweeds contain a large fraction of carbohydrates that are a promising source for enzymatic and/or microbial biorefinery conversions. The thermoanaerobe Thermoanaerobacterium AK17 is a versatile fermentative bacterium producing ethanol, acetate and lactate from various sugars. In this study, strain AK17 was engineered for more efficient production of ethanol by knocking out the lactate and acetate side-product pathways. This was successfully achieved, but the strain reverted to acetate production by recruiting enzymes from the butyrate pathway. Subsequently this pathway was knocked out and the resultant strain AK17_M6 could produce ethanol close to the maximum theoretical yield (90%), leading to a 1.5-fold increase in production compared to the wild-type strain. Strain AK17 was also shown to successfully ferment brown seaweed hydrolysate from Laminaria digitata to ethanol in a comparatively high yield of 0.45 g/g substrate, with the primary carbon sources for the fermentations being mannitol, laminarin-derived glucose and short laminari-oligosaccharides. As strain AK17 was successfully engineered and has a wide carbohydrate utilization range that includes mannitol from brown seaweed, as well as hexoses and pentoses found in both seaweeds and lignocellulose, the new strain AK17_M6 obtained in this study is an interesting candidate for production of ethanol from both second and third generations biomass.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	2731-3654 2731-3654 1754-6834
DOI:	10.1186/s13068-023-02388-y