Extracted sweet sorghum substrates as a source of fermentable sugars

Abstract

Simple sugars of variously prepared sweet sorghum culms were extracted to different extents depending upon water temperature, extraction time, and size of the culm substrate. Sonication of succulent culms (≤15 mm split sections) suspended in water followed by centrifugation extracted 88% of the available sugars. However, hot water extraction of freeze-dried and milled sorghum quantitatively extracted the simple sugars, which were 2/3 sucrose and 1/3 glucose and fructose. Following the sugar removal, the residue was extracted with a 12% NaOH solution to leave a cellulosic residue that was nearly quantitatively converted (98%) to glucose by enzymatic hydrolysis. Ninety percent of the pentosans in the culms were extracted by the alkali treatment, and then 91% of these pentosans were precipitated from the alkaline extract with acidified ethanol.