Agro-industrial potential of sweet sorghum accessions grown under semi-arid conditions
The current world-wide interest in alternative and sustainable forms of energy is providing an opportunity for carving new pathways of development in many countries. Plants are particularly attractive vehicles in this regard because of their innate capacity to self-renew and to produce chemical forms of energy every time. Carbohydrates and oils as primary products from plants are attractive raw materials for the production of alternative forms of energy such as bioethanol and biodiesel. Against this background, this study was undertaken to assess the potential of sweet sorghum as a feedstock for bioethanol production. To this end, a comparative analysis of non-structural carbohydrate amounts in mature stems of several local accessions of sweet sorghum was carried out. For comparison, the same products were also determined in mature stems of sugarcane. Sucrose was the predominant sugar in the mature stems of sweet sorghum as was the case with sugarcane. However, the overall carbohydrate profiles of sweet sorghum were markedly different from those of sugarcane. Mature stems of sweet sorghum contain more readily fermentable sugars than mature sugarcane stems. In addition, sweet sorghum also accumulates starch in the stems as well as in the seeds. Through hydrolysis, this serves as an additional source of glucose for fermentation into ethanol. These data clearly demonstrate the renewable energy resource potential of sweet sorghum. Nonetheless, further studies on the basic biology of carbohydrate partitioning in sweet sorghum are warranted. Such studies could provide rational basis for improvement of wet-fermentation substrate yield of this crop.
Key words: Metabolism, non-structural carbohydrates, renewable energy, substrates, sucrose, trade-offs, wet fermentation.