Date Published: May 23, 2019
Publisher: Public Library of Science
Author(s): Alberto Acevedo, Rachael Simister, Simon J. McQueen-Mason, Leonardo D. Gómez, Igor Cesarino.
Sudangrass, Sorghum sudanense (Piper) Stapf, is a vigorous forage crop that has also been used for biogas, paper, and electricity production. Due to the large biomass yields achieved by sudangrass and the large area of potential growth in Argentina seven sudangrass accessions from a collection of S. sudanense were analyzed to evaluate their potential as feedstocks for lignocellulosic bioethanol production, and to assess whether there is an association between the response to biotic and abiotic stresses and the composition of the biomass. The biomass composition was analyzed for major cell wall polymers, monosaccharides, and elemental composition. On average, 68% of stem lignocellulosic biomass was comprised of matrix polysaccharides and crystalline cellulose, representing a potential source of sugars for bioethanol production. Xylose was the predominant matrix polysaccharide monosaccharide comprising, on average, 45% of the total sugars, followed by arabinose, glucose, galactose, galacturonic acid, mannose, glucuronic acid, and fucose. Rhamnose was not detected in any of the biomasses analyzed. Silica was the most abundant element in sudangrass stem, followed by chloride, calcium, phosphorus and sulfur. We performed saccharification analyses after pretreatments. Alkaline pretreatment was more effective than water pretreatment. Sodium hydroxide pretreatment exposed different levels of recalcitrance among sudangrass accessions, whereas the water pretreatment did not. Phenological traits were also evaluated, showing significant variability among accessions. The comparison of major cell wall polymers and monosaccharide composition between tolerant and susceptible accessions to abiotic and biotic stresses suggests an association between the composition of the biomass and the response to stress.
Argentina is a large country (3.761.274 km2) and has a range of different climates and soils. Despite this environmental diversity, only three crops stand as feedstocks for biofuel production in the country. Corn and sugarcane are used as feedstocks for first generation (1G) bioethanol production and soybean is used as feedstock for biodiesel production. Together they account for more than 90% of both the productivity and the planted area estimated for 2019 . Independently of the market to which these crops are destined for, it would be highly desirable to increase the diversity of feedstocks in terms of the productivity and planted area. Argentina has a number of industrial plants that produce 1G bioethanol but currently there is no production of second generation (2G) bioethanol. Given the biomass production in the country, there is a possibility of establishing 2G bioethanol production. Besides policy, investment and demand/supply chains, one important issue in this area is the prospection of suitable biomass feedstock.
Germplasm collections are important sources of genetic variability. Investigating the genetic, biochemical and agronomical features, and the bioenergy potential of the accessions comprising any germplasm collection underscores and justifies their conservation. Sorghum sudanense is a versatile species: the whole plant can be used in grazing, hay or silage. Identifying other uses beyond forage, would add alternatives to the agronomical systems where this crop is incorporated and provide extra income for farmers. To this end, seven sudangrass accessions, randomly chosen from a collection of sorghum germplasm, were analyzed to evaluate their potential as feedstocks for lignocellulosic bioethanol production, and to assess whether there is a correlation between the response to biotic and abiotic stresses and the composition of the biomass.