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The article presents a study on the genotypic variations in the non-structural carbohydrate (NSC) and cell-wall components of rice, sorghum and sugar cane stems. It mentions that the genotypic variations are determined to examine the potential use of such crops for bioethanol production. It notes that rice contains less lignin compared to other crops, which shows high potential for the efficient saccharification of cellulose.

The article presents a study on the recovery of glucose and fructose through enzymatic saccharification of rice straw with soft carbohydrates. It mentions that the study investigated the amounts of soft carbohydrates that can be found in rice straw. Furthermore, it introduces the development of a method to easily extract glucose and fructose including the use of heat-pretreatment. It also notes that 43.5 percent is the maximum yields of glucose and fructose in rice straw per dry weight.

Recently developed high-yielding rice varieties with extra-large sink capacity often have unstable grain filling. Therefore, understanding the factors that limit grain filling is essential for further improvement of rice grain yield. Because grain-filling is determined by the complex sink–source balance, grain-filling ability is very difficult to evaluate. In this study, we compared grain-filling-related traits of three high-yielding cultivars with high sink capacity. We found that the translocation of non-structural carbohydrates (NSC) from stem to panicle during early ripening and grain filling was significantly lower in Momiroman than in Hokuriku 193 and Teqing, whereas dry matter accumulation of the whole plant did not differ among the cultivars throughout ripening. The NSC-components, sucrose and starch were both remained higher in stems of Momiroman than other cultivars. ADP-glucose pyrophosphorylase (AGPase; EC 2.7.7.27) activity was not enhanced and α-Amylase (EC 3.2.1.1) and β-Amylase (EC 3.2.1.2) activities were not impeded in the stems. These data suggested lower sucrose translocation is responsible for lower NSC translocation in Momiroman, rather than too high starch synthesis and too low starch degradation activities. At early ripening, grain growth of the superior spikelets was slow in Momiroman even if carbon supply was increased by spikelet-thinning treatments. These results raise the possibility that low sink strength determines low grain filling in Momiroman, which delays grain growth and decreases sucking force of NSC from the stem. [ABSTRACT FROM AUTHOR]

Highlights: [•] We examined yield potential and the constraints of the high-yielding varieties. [•] Grain yields of high-yielding varieties were greater than that of reference variety. [•] The main factor for the high yield was remarkably large sink capacity. [•] Indica-dominant varieties showed superior grain-filling ability. [•] Factors for the varietal difference were investigated. [ABSTRACT FROM AUTHOR]

Abstract: A simple process (the direct-saccharification-of-culms (DiSC) process) to produce ethanol from rice straw culms, accumulating significant amounts of soft carbohydrates (SCs: glucose, fructose, sucrose, starch and β-1,3-1,4-glucan) was developed. This study focused on fully mature culms of cv. Leafstar, containing 69.2% (w/w of dried culms) hexoses from SCs and cellulose. Commercially-available wind-separation equipment successfully prepared a culm-rich fraction with a SC recovery of 83.1% (w/w) from rice straw flakes (54.1% of total weight of rice straw). The fraction was suspended in water (20%, w/w) for starch liquefaction, and the suspension was subjected to a simultaneous saccharification and fermentation with yeast, yielding 5.6% (w/v) ethanol (86% of the theoretical yield from whole hexoses in the fraction) after 24h fermentation. Thus, the DiSC process produced highly-concentrated ethanol from rice straw in a one vat process without any harsh thermo-chemical pretreatments. [Copyright &y& Elsevier]

Abstract: The major carbohydrates of rice straw samples were determined in order to evaluate the potential of using rice straw as a feedstock for ethanol production in Japan. Straw samples were harvested by cutting the plants at ground level when the grain was mature and immediately heating or chilling the samples. In all cases, significant amounts (62–303 g kg−1) of soft carbohydrates defined as consisting of glucose, fructose, sucrose, starch and β-1,3-1,4-glucan were detected, in addition to structural carbohydrates (cellulose and xylan). These results indicate that rice straw is a rich source of fermentable sugars from both soft carbohydrates and lignocellulosic portions of the cell wall. [Copyright &y& Elsevier]