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Abstract: Energycane (Saccharum hyb.) is a perennial bioenergy crop derived from sugarcane, but with higher fiber, greater biomass yields, and better cold tolerance than typical sugarcane. Two commercial sugarcanes, two high-sugar (Type I) energycanes, and five high-fiber (Type II) energycanes were planted at Tifton, GA, USA in a randomized complete block design with four replications. Beginning in October, 2008 (plant-cane crop year) five monthly samples were taken to assess the effects of delaying harvest on biomass composition and quality for ethanol production. The monthly harvests were repeated in the winter of 2010–2011 (second-ratoon crop year). Delaying harvest into the winter months resulted in minimal reductions in biomass moisture and N mass fractions, while K mass fraction decreased significantly. Free sugar mass fraction also decreased, thus causing the biomass to have an apparent increase in relative mass fractions of ash and neutral detergent fiber (NDF). The reduction in free sugars was more pronounced in the colder harvest season (2010–2011). The composition of biomass fiber (cellulose, hemicellulose, and lignin) was generally stable over time. A bench-top partial saccharification and co-fermentation (PSCF) protocol employing xylose-fermenting Escherichia coli was used to assess ethanol yields from the sequentially harvested biomass. Ethanol yield from sugarcanes and Type I energycanes was more variable over time, due to degradation of free sugars. Thus, early harvest is recommended to avoid loss of fermentable sugars. Type II energycanes can be harvested later during the winter months with little change in conversion properties. [Copyright &y& Elsevier]

Estimation methods and evaluation of ethanol yield from sweet sorghum ( Sorghum bicolor (L.) Moench) based on agronomic production traits and juice characteristics is important for developing parents and inbred lines of sweet sorghum that can be used by the bio-ethanol industry. The objectives of this study were to compare published indirect methods for the calculation of ethanol yields from sweet sorghum and test them against direct ethanol production in laboratory, as well as to determine the relationships among total soluble sugar and juice traits with ethanol concentrations over time. Four sorghum varieties (KKU40, Theis, BJ248 and SPV1411) were compared for juice characters and ethanol yield in a randomized complete block design with four replications. Agronomic and juice traits of sweet sorghum were recorded during flowering and at harvest. Juice of sweet sorghum was fermented by yeast ( Saccharomyces cerevisiae ) to obtain ethanol yields in the laboratory, which were then compared with ethanol yields calculated based upon five calculation methods from the literature. Ethanol yield estimates calculated from published methods were generally higher than laboratory values. However, estimates based upon Somani and Taylor (2003) and on Smith et al. (1987) when multiplying theoretical yields by 80% were not significantly different from laboratory results. Though ethanol yield are strongly correlated with sugar yields, juice traits influenced the rate of fermentation of sugars over time. For example, glucose, fructose and nitrogen content in the juice had a positive effect on ethanol concentration after 12 h of fermentation while multiple juice traits were significantly associated with ethanol concentrations after 24, 36 and 48 h of fermentation. [ABSTRACT FROM AUTHOR]

Abstract: Pretreatment of grasses is required to maximize ethanol yield during fermentation. T85 bermudagrass and Merkeron napiergrass (Pennisetum purpureum Schumach.) were either left untreated or were pressurized batch hot water (PBHW) pretreated for 2 min at 230 °C at 5% w/v whole grass solids loading. Following a 24 h enzymatic digestion, untreated and PBHW pretreated grasses were evaluated for ethanol production and co-product generation including potential fermentation inhibitors. Fermentations of PBHW pretreated grasses with E. coli LY01 produced twice the ethanol of their untreated counterparts. PBHW pretreated Merkeron napiergrass produced 224.5 mg/g grass ethanol (73% maximum theoretical yield) and PBHW pretreated T85 bermudagrass reached 213.0 mg/g grass (70% maximum theoretical ethanol yield). Pretreatment by PBHW resulted in increased solubilization of hemicelluloses. PBHW pretreatment also produced potential fermentation inhibitors such as acetic, formic, cinnamic acids, and aldehydes. Despite some of these inhibitors remaining with the solids after PBHW pretreatment, there was more efficient hydrolysis of the cellulose and remaining hemicellulose during the enzymatic digestion of the grasses prior to fermentation when compared to the untreated grasses. This increase in digestibility observed with enzymes prior to fermentation resulted in increased ethanol yields during bioconversion using E. coli LY01 as the biocatalyst. [Copyright &y& Elsevier]