Conversion of Carbohydrates in Lignocellulosic Biomass after Chemical Pretreatment

The aim of the study was to determine the quantitative and qualitative changes taking place in biomass components actively participating in methane fermentation, i.e., in carbohydrates, as a result of chemical pretreatment. Analyses were conducted on agricultural waste (corn stover, also called corn straw, and corncobs) as materials most commonly used in methane fermentation, as well as poplar wood, a material relatively rarely used in biogas production. Pretreatment with the aim of increasing efficiency of methane fermentation was carried out with the use of acid and alkaline solutions of different concentrations. The effect of pretreatment on carbohydrates was analyzed based on the quantitative and qualitative changes in this component. Due to the structural heterogeneity of carbohydrates, their varied reactivity and fermentability were determined in terms of holocellulose, cellulose, and pentosans. The chemical structure of cellulose was also analyzed. It is shown in this study that chemical pretreatment causes transformations of carbohydrate components, which differ quantitatively and qualitatively in the compared raw materials. It was found that the alkaline treatment caused smaller changes in the percentage shares of the carbohydrate biomass components as compared to the acid treatment. Moreover, it was observed that the compared materials differ in terms of quantitative changes in their chemical composition depending on the composition of the raw material prior to pretreatment. In the case of corn waste subjected to the action of 1 and 3% NaOH, the share of pentosans in the biomass increased. It was established that this is a change with a positive effect on fermentation efficiency. The action of acids and alkalis on the biomass led to similar structural changes in cellulose, which are adverse for the fermentation process.

USING OF BIOMASS AND WASTES OF BEANS (PHASEOLUS VULGARIS) AND PEAS (PISUM SATIVUM) PRO-CESSING AS SORPTION MATERIAL FROM POLLUTANTS REMOVING FROM WATER ENVIRONMENTS (LIT-ERATURE REVIEW)

Was reported literature findings of domestic and foreign articles about using of biomass components (leaves, straw, pods, seeds) and wastes of beans (Phaseolus vulgaris) and peas (Pisum sativum) pods shells processing as sorption material for pollutants (metals ions, colorants) removing from water environments. Concise literature findings about Pisum sativum and Phaseolus vulgaris plant structure, cultivation value, and chemical composition of some biomass components are described. Was revealed that composition of beans and peas pods has big amount of proteins, that can provide removing of metals ions such as (Cd(II), Co(II), Cr(III) и Cr(VI), Cu(II), Fe(III), Mo(VI), Ni(II), Pb(II), Sb(III) и Sb(V), Zn(II)) from water environments. Was showed the possibility of sorption characteristics increase for pollutants by Phaseolus vulgaris and Pisum sativum biomass treatment with different chemical reagents. Was revealed that pollutants sorption isotherms of wastes and biomass of considered legumes are described mostly by Langmuir model than by Freundlich model. The kinetic of process mostly match to pseudo-second order model. It is shown that using of seeds and pods shells of legumes is prospectively for removing of heavy metals ions and suspended particles from water. Was proposed to use charcoal, which was gotten by peas pods carbonization for removing of heavy metals ions from water environments. Concluded, that using of legumes pods extracts is more effective for clearing water environments from heavy metals ions.

Allometric Models for Estimating Aboveground Biomass in Short Rotation Crops of Acacia Species in Two Different Sites in Chile

We evaluated the ability of different allometric models to estimate the biomass production of short-rotation woody crops of Acacia dealbata, A. mearnsii and A. melanoxylon. Models considered the adjustment and validation of biomass functions and biological restrictions, such as the use of additive components of the biomass (stem, branches, and leaves). Adjustments of linear and nonlinear models of the three acacia species—established in two locations and of three densities in southern Chile—were utilized. Systems of equations were adjusted to guarantee the addition of the biomass components and the trees’ total biomass. The selection of models was performed based on their goodness of fit and predictive quality. Methods that accounted for the correlation between biomass components granted an additively consistent equations system with efficient estimates and reliable prediction intervals.

Challenges and Perspective of Recent Biomass Pretreatment Solvents

The increased demands on renewable and sustainable products require enhancing the current conversion efficiency and expanding the utilization of biomass from a single component (i.e., cellulose) to entire biomass components in the biorefinery concept. Pretreatment solvent plays a critical role in various biorefinery processes. Recent pretreatment solvents such as organic co-solvents, acid hydrotropes, ionic liquids and deep eutectic solvents showed effective biomass fractionation as well as preservation of high-quality cellulose and lignin under mild conditions. Despite these significant enhancements in biomass pretreatment solvent, there are still many challenges, such as feedstock variety, valorization of non-cellulose components, and eco-friendliness of the applied catalyst and solvent. These technical, economic and environmental obstacles should be considered in future biomass pretreatment solvents. In particular, the development of feedstock-agnostic solvent with high fractionation performance for high quality and quantity of all three major components (i.e., cellulose, hemicellulose, and lignin) together would be an ideal direction.

Kinetics of the ancestral carbon metabolism pathways in deep-branching bacteria and archaea

The origin of life is believed to be chemoautotrophic, deriving all biomass components from carbon dioxide, and all energy from inorganic redox couples in the environment. The reductive tricarboxylic acid cycle (rTCA) and the Wood–Ljungdahl pathway (WL) have been recognized as the most ancient carbon fixation pathways. The rTCA of the chemolithotrophic Thermosulfidibacter takaii, which was recently demonstrated to take place via an unexpected reverse reaction of citrate synthase, was reproduced using a kinetic network model, and a competition between reductive and oxidative fluxes on rTCA due to an acetyl coenzyme A (ACOA) influx upon acetate uptake was revealed. Avoiding ACOA direct influx into rTCA from WL is, therefore, raised as a kinetically necessary condition to maintain a complete rTCA. This hypothesis was confirmed for deep-branching bacteria and archaea, and explains the kinetic factors governing elementary processes in carbon metabolism evolution from the last universal common ancestor.