Selection of yeast strains for bioethanol production from UK seaweeds

Abstract

Macroalgae (seaweeds) are a promising feedstock for the production of third generation bioethanol, since they have high carbohydrate contents, contain little or no lignin and are available in abundance. However, seaweeds typically contain a more diverse array of monomeric sugars than are commonly present in feedstocks derived from lignocellulosic material which are currently used for bioethanol production. Hence, identification of a suitable fermentative microorganism that can utilise the principal sugars released from the hydrolysis of macroalgae remains a major objective. The present study used a phenotypic microarray technique to screen 24 different yeast strains for their ability to metabolise individual monosaccharides commonly found in seaweeds, as well as hydrolysates following an acid pre-treatment of five native UK seaweed species (Laminaria digitata, Fucus serratus, Chondrus crispus, Palmaria palmata and Ulva lactuca). Five strains of yeast (three Saccharomyces spp, one Pichia sp and one Candida sp) were selected and subsequently evaluated for bioethanol production during fermentation of the hydrolysates. Four out of the five selected strains converted these monomeric sugars into bioethanol, with the highest ethanol yield (13 g L−1) resulting from a fermentation using C. crispus hydrolysate with Saccharomyces cerevisiae YPS128. This study demonstrated the novel application of a phenotypic microarray technique to screen for yeast capable of metabolising sugars present in seaweed hydrolysates; however, metabolic activity did not always imply fermentative production of ethanol.

A Brief Review of Anaerobic Digestion of Algae for Bioenergy

“…Algal polysaccharide composition is often different from that of terrestrial plants with the most important polysaccharides of brown algae being Laminarin, Mannitol, Alginate and Fucoidan [151]. Algae can also typically contain a more diverse range of monomeric sugars than terrestrial plants [152]. Algal polysaccharides are further discussed in Section 5.3.…”

Cellulase and acid-catalysed hydrolysis of Ulva fasciata, Hydropuntia dentata and Sargassum vulgare for bioethanol production

“…The total carbohydrates fraction in seaweeds and most biomass are made up of various monomeric sugars (reducing sugars). Seaweeds are known to be composed of a broad diversity of monomeric sugars or monosaccharides as compared to other biomass such as cassava, sugarcane and elephant grass used in bioethanol production [28]. This study found the major monomeric sugars in U. fasciata to be glucose, xylose and rhamnose at 15.1, 7.6 and 5.4%, respectively; S. vulgare had glucose and fucose at 15.3 and 4.0%, respectively; and H. dentata had galactose and glucose at 13.1 and 12.0%, respectively, of dry biomass (Table 3).…”

Experimental processing of seaweeds for biofuels

“…The genomic integration and overexpression of the gene encoding alginate monomer (4‐deoxy‐ l ‐erythro‐5‐hexoseulose uronate) transporter from the alginolytic eukaryote Asteromyces cruciatus enabled S. cerevisiae to ferment this monomer and produce bioethanol (Enquist‐Newman et al, ). For the screening and selection of yeast strains capable to metabolize a range of monosaccharides originating from the breakdown of macroalgal polysaccharides, a phenotypic microarray (metabolic output of yeast strains grown on synthetic minimal media with different carbon sources) can be applied (Kostas et al, ). An interesting study was presented by Khambhaty et al () who proposed for the first time the isolation, characterization and utilization of marine yeast ( Candida sp.)…”