The members of the genus Miscanthus are potential feedstocks for biofuels because of the promising high yields of biomass per unit of planted area. This review addresses species, cultivation, and lignocellulose composition of Miscanthus, as well as pretreatment and enzyme saccharification of Miscanthus biomass for ethanol fermentation. The average cellulose contents in dried biomass of Miscanthus floridulus, Miscanthus sinensis, Miscanthus sacchariflorus, and Miscanthus × giganteus (M × G) are 37.2, 37.6, 38.9, and 41.1% wt/wt, respectively. A number of pretreatment methods have been applied in order to enhance digestibility of Miscanthus biomass for enzymatic saccharification. Pretreatment of Miscanthus using liquid hot water or alkaline results in a significant release of glucose; while glucose yields can be 90% or higher if a pretreatment like AFEX that combines both chemical and physical processes is used. As ethanol is produced by yeast fermentation of the hydrolysate from enzymatic hydrolysis of residual solids (pulp) after pretreatment, theoretical ethanol yields are 0.211-0.233 g/g-raw biomass if only cellulose is taken into account. Simultaneous saccharification and fermentation of pretreated M × G and M. lutarioriparius results in experimental ethanol yields of 0.13 and 0.15 g/g-raw biomass, respectively. Co-production of value-added products can reduce the overall production cost of bioethanol.
Water-soluble organic matters (WSOMs) play an important role in determining magnitudes of climatic and environmental impacts of organic aerosol particles because of their contributions to hygroscopic growth and cloud formation. These processes are dependent on water solubility as well as distribution of this property in a particle, yet no method has been available to quantify such characteristics. In this study, we developed a theoretical framework to classify WSOM by 1-octanolwater partitioning that has a strong correlation with water solubility. 1-octanol-water partitioning coefficient also has a strong correlation with a traditional solid phase extraction method, facilitating interpretation of data from the technique. The theoretical analysis demonstrated that the distributions of WSOM classified by 1-octanol-water partitioning depend on (1) the volume ratio of 1-octanol and aqueous phases, and (2) extraction steps. The method was tested by using organic aerosol particles generated by smoldering of a mosquito coil, which serves as a surrogate for biomass burning particles. The WSOM extracted from the mosquito coil burning particles was classified by 1-octanol-water partitioning at different volume ratios. These solutions, including both the 1-octanol and aqueous phases, were nebulized to generate particles for measurements using an online aerosol mass spectrometer. The mass spectra indicated that highly oxygenated species tend to be highly soluble, while high molecular weight compounds are less soluble. Linear combinations of these mass spectra allowed the estimation of the mass fractions of WSOM partitioned to 1octanol and aqueous phases, thereby facilitating the evaluation of the mass fractions of cloud condensation nuclei (CCN) active materials.
Abstract. The relationship between hygroscopic properties and chemical characteristics of Indonesian biomass burning (BB) particles, which are dominantly generated from peatland fires, was investigated using a humidified tandem differential mobility analyzer. In addition to peat, acacia (a popular species at plantation) and fern (a pioneering species after disturbance by fire) were used for experiments. Fresh Indonesian peat burning particles are almost non-hygroscopic (mean hygroscopicity parameter, κ < 0.06) due to predominant contribution of water-insoluble organics. The range of κ spans from 0.02 to 0.04 (dry diameter = 100 nm, hereinafter) for Riau peat burning particles, while that for Central Kalimantan ranges from 0.05 to 0.06. Fern combustion particles are more hygroscopic (κ = 0.08), whereas the acacia burning particles have a mediate κ value (0.04). These results suggest that κ is significantly dependent on biomass types. This variance in κ is partially determined by fractions of water-soluble organic carbon (WSOC), as demonstrated by a correlation analysis (R = 0.65). κ of water-soluble organic matter is also quantified, incorporating the 1-octanolwater partitioning method. κ values for the water extracts are high, especially for peat burning particles (A 0 (a whole part of the water-soluble fraction): κ = 0.18, A 1 (highly watersoluble fraction): κ = 0.30). This result stresses the importance of both the WSOC fraction and κ of the water-soluble fraction in determining the hygroscopicity of organic aerosol particles. Values of κ correlate positively (R = 0.89) with the fraction of m/z 44 ion signal quantified using a mass spectrometric technique, demonstrating the importance of highly oxygenated organic compounds to the water uptake by Indonesian BB particles. These results provide an experimentally validated reference for hygroscopicity of organicsdominated particles, thus contributing to more accurate estimation of environmental and climatic impacts driven by Indonesian BB particles on both regional and global scales.
A method for the production of high-purity isomalto-oligosaccharides (IMO) involving the transglucosylation by transglucosidase and yeast fermentation was proposed. The starch of rice crumbs was enzymatically liquefied and saccharified, and then converted to low-purity IMO syrup by transglucosylation. The low-purity IMO produced either from rice crumbs or tapioca flour as the starch source could be effectively converted to high-purity IMO by yeast fermentation to remove the digestible sugars including glucose, maltose, and maltotriose. Both Saccharomyces carlsbergensis and Saccharomyces cerevisiae were able to ferment glucose in the IMO syrup. Cells of S. carlsbergensis harvested from the medium of malt juice were also able to ferment maltose and maltotriose. A combination of these two yeasts or S. carlsbergensis alone could be used to totally remove the digestible sugars in the IMO, coupled with the production of ethanol. The resultant high-purity IMO, including mainly isomaltose, panose, and isomaltotriose made up more than 98% w/w of the total sugars after a 3-day fermentation. When the low-purity IMO was produced from the starch of tapioca flour, 3-day fermentation under the same conditions resulted in IMO with purity lower than that from rice crumbs. For low-purity IMO from rice crumbs, fermentation with washed S. carlsbergensis cells harvested at log phase was the most effective. However, for the low-purity IMO from tapioca flour, incubation with S. cerevisiae for the first 24 h and then supplementing with an equal amount of S. carlsbergensis cells for further fermentation was the most effective approach for producing high-purity IMO.
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