Abstract
Brown algae is a kind of renewable resource for biofuels production. As the major component of carbohydrate in the cell walls of brown algae, alginate can be degraded into unsaturated monosaccharide by exo-type alginate lyases, then converted into 4-deoxy-L-erythro-5-hexoseulose uronate (DEH) by a non-enzyme reaction, which is an important raw material for the preparation of bioethanol. In our research, a novel exo-type alginate lyase, VsAly7D, belonging to the PL7 family was isolated from marine bacterium Vibrio sp. QY108 and recombinantly expressed in Escherichia coli. The purified VsAly7D demonstrated the highest activity at 35 °C, whereas it still maintained 46.5% and 83.1% of its initial activity at 20 °C and 30 °C, respectively. In addition, VsAly7D exhibited the maximum activity under alkaline conditions (pH 8.0), with the simultaneously remaining stability between pH 8.0 and 10.0. Compared with other reported exo-type enzymes, VsAly7D could efficiently degrade alginate, poly-β-D-mannuronate (polyM) and poly-α-L-guluronate (polyG) with highest specific activities (663.0 U/mg, 913.6 U/mg and 894.4 U/mg, respectively). These results showed that recombinant VsAly7D is a suitable tool enzyme for unsaturated alginate monosaccharide preparation and holds great promise for producing bioethanol from brown algae.
Highlights
Due to the deepening problem of resource depletion, macroalgae and microalgae are drawing more attention from researchers owing to their excellent properties as renewable and environmentally friendly feedstocks to produce biofuels [1,2]
The exploration of macroalgae and microalgae can relieve the conflict between food and fuels and provide many byproducts, such as edible proteins for poultry [4]
QY108 consisted of an open reading frame (ORF) of 1044 bp and encoded protein VsAly7D, containing 347 amino acid residues
Summary
Due to the deepening problem of resource depletion, macroalgae and microalgae are drawing more attention from researchers owing to their excellent properties as renewable and environmentally friendly feedstocks to produce biofuels [1,2]. Different from terrestrial crops, macroalgae grow in sea water, avoiding the consumption of fresh water, arable soils or fertilizers, and can mitigate atmospheric CO2 [3]. The exploration of macroalgae and microalgae can relieve the conflict between food and fuels and provide many byproducts, such as edible proteins for poultry [4]. As a species of macroalgae, exists extensively in the ocean. Alginate is the major polysaccharide composition of marine brown macroalgae, accounting for about 40% of the dry weight of the biomass [5]. Based on the differences of the monomers, alginate is divided into poly-αL-guluronate (polyG), poly-β-D-mannuronate (polyM) and a heteropolymer (polyMG) [6]
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