Bioconversion of agricultural lignocellulosic residues into branched-chain fatty acids usingStreptomyces lividans

Abstract

-Two lignocellulosic agricultural residues, sunflower stalks and rape straw, were investigated as potential low-cost, non-food substrates for the production of triacylglycerols by the oleaginous, lignocellulolytic bacteria Streptomyces lividans. Chemical analysis of each type of residue revealed similar cell wall compositions in the polysaccharides and lignins of the two feedstocks, with high lignin β-O-4 bond content compared to other angiosperms' lignin. Growing tests of Streptomyces lividans TK 24 were performed before and after sequential water and ethanol extraction by assessing bacterial fatty acid accumulation. All extracted and non-extracted samples were found to be substrates of the bacteria with fatty acid production ranging between 19% and 44% of the production obtained with arabinose as a reference substrate. The maximum conversion rate was obtained with the less lignified, non-extracted sample. This study suggests that lignocellulosic residues from oleaginous crops could be advantageously valorized by microbial bioconversion processes for the production of lipids of interest.Keywords: Streptomyces / rapeseed / sunflower / fatty acids / lignocellulose Résumé -Deux types de résidus issus de l'agriculture, des tiges de tournesol et des pailles de colza, ont été étudiés afin d'évaluer leur potentiel comme substrat non alimentaire et à faible coût pour la production de triacylglycérol par Streptomyces lividans, une bactérie oléagineuse et lignocellulolytique. Une analyse chimique de chaque résidu a montré une composition des parois en polysaccharides et lignines identique avec un fort taux de liaison β-O-4, contrairement aux lignines des autres angiospermes. Des tests de croissance de la souche TK24 de Streptomyces lividans ont été effectués sur les résidus avant et après extraction séquentielle à l'eau et à l'éthanol. La croissance a été évaluée en mesurant l'accumulation des acides gras bactériens. Tous les résidus se sont révélés être des substrats pour la bactérie, avec une production allant de 19% à 44% de la production de référence obtenue sur arabinose. Le maximum de conversion a été obtenu sur le résidu le moins lignifié et non extrait. Cette étude suggère que les résidus lignocellulosiques des plantes oléagineuses de grande culture peuvent être valorisés de manière avantageuse en lipides d'intérêt par des procédés de bioconversion microbiologique.

Phytomanagement and Remediation of Cu-Contaminated Soils by High Yielding Crops at a Former Wood Preservation Site: Sunflower Biomass and Ionome

“…Shoots and seed hulls can be merged with other lots and used by various sectors processing non-food crops such as (1) biorefineries for bio-oil (Casoni et al, 2015), biofuel (Ziebell et al, 2013;Zhao et al, 2016) and bioethanol (Dhiman et al, 2017) via the production of fermentable sugars (Ruiz et al, 2013;Liguori et al, 2016;Tavares et al, 2016), (2) bioconversion into branched-chain fatty acids (Dulermo et al, 2016) (3) solid fuel production (Alaru et al, 2013), (4) syngas and biogas production (Zabaniotou et al, 2010;Graß et al, 2013;Hesami et al, 2015), (5) energy production by co-firing with coal (Kułazynski et al, in press), (6) organic fertilizers for marginal land and Cu-deficient soils as compost or biochar amendment (Evangelou et al, 2015;Colantoni et al, 2016;Saleh et al, 2016); and (7) insulation ecomaterial and biocomposites (Mati-Baouche et al, 2016;Liu et al, 2017;Brouard et al, 2018).…”

Streptomyces spp. as biocatalyst sources in pulp and paper and textile industries: Biodegradation, bioconversion and valorization of waste

“…Additionally, in the food waste valorization field, an immobilized polygalacturonase from S. halstedii ATCC 10897 was used in a bioreactor for the degradation of pear and cucumber residues increasing the sugar content up to 15.33 and 9.35 mg/mL, respectively (Ramírez‐Tapias et al, 2018 ). Another application for lignocellulosic bioconversion was developed for the generation of branched‐chain fatty acids for lipid‐based biofuel applications where S. lividans bioconverted sunflower stalks and rape straw residues into triacylglycerols with a yield of 19%–44% conversion (Dulermo et al, 2016 ). Therefore, exploring enzymes from Streptomyces spp.…”

Production of neo acids from biomass-derived monomers

“…9 However, these processes are not economical and suffer from scalability issues. Microbial fermentation has been explored to produce branched carboxylic acids derived from biomass, [18][19][20] but the process is challenged by long fermentation time, selectivity, and enzyme inactivation. Li et al described the chemical synthesis of medium-chain carboxylic acids from cellulose-derived platform chemicals (Scheme 1C).…”