A Bibliometric Analysis of Global Fine Roots Research in Forest Ecosystems during 1992–2020

(1) Background: Fine roots (≤2 mm in diameter) play a critical role in forest ecosystem ecological processes and has been widely identified as a major research topic. This study aimed to synthesize the global literature based on the Web of Science Core Collection scientific database from 1992 to 2020 and summarize the research trends and prospects on research of fine roots in forest ecosystems. A quantitative bibliometric analysis was presented with information related to authors, countries, institutions, journals, top cited publications, research hotspots, trends, and prospects. (2) Results: The results showed that the amount of publications has increased exponentially. USA, China, and Germany were the most productive countries. Chinese Academy of Science was the most productive institution on fine roots research and also has a key position in both domestic and international cooperation networks. Leuschner C and Hertel D were the most productive authors. Six core journals were confirmed from 471 journals based on Bradford’s law. The distribution of the frequency of authors and the number of their publications were fitted with Lotka’s Law. Author collaboration network was mainly limited in the same countries/territories and institutions. Keywords analysis indicates that the hotspots are biomass, decomposition, and respiration of fine roots, especially under climate change. (3) Conclusion: Our results provide a better understanding of global characteristics and trends of fine roots that have emerged in this field, which could offer reference for future research.

Early nitrogen supply as an alternative management for a cover crop-maize sequence under a no-till system

Optimizing agronomic efficiency (AE) of nitrogen (N) fertilizer use by crops and enhancing crop yields are challenges for tropical no-tillage systems since maintaining crop residues on the soil surface alters the nutrient supply to the system. Cover crops receiving N fertilizer can provide superior biomass, N cycling to the soil and plant residue mineralization. The aims of this study were to (i) investigate N application on forage cover crops or cover crop residues as a substitute for N sidedressing (conventional method) for maize and (ii) investigate the supply of mineral N in the soil and the rates of biomass decomposition and N release. The treatments comprised two species, i.e., palisade grass [Urochloa brizantha (Hochst. Ex A. Rich.) R.D. Webster] and ruzigrass [Urochloa ruziziensis (R. Germ. and C.M. Evrard) Crins], and four N applications: (i) control (no N application), (ii) on live cover crops 35 days before maize seeding (35 DBS), (iii) on cover crop residues 1 DBS, and (iv) conventional method (N sidedressing of maize). The maximum rates of biomass decomposition and N release were in palisade grass. The biomass of palisade grass and ruzigrass were 81 and 47% higher in N application at 35 DBS compared with control in ruzigrass (7 Mg ha−1), and N release followed the pattern observed of biomass in palisade and ruzigrass receiving N 35 DBS (249 and 189 kg N ha−1). Mineral N in the soil increased with N application regardless of cover crop species. Maize grain yields and AE were not affected when N was applied on palisade grass 35 DBS or 1 DBS (average 13 Mg ha−1 and 54 kg N kg−1 maize grain yield) compared to conventional method. However, N applied on ruzigrass 35 DBS decreased maize grain yields. Overall, N fertilizer can be applied on palisade grass 35 DBS or its residues 1 DBS as a substitute for conventional sidedressing application for maize.

Efek Zeolit untuk Produksi Tar dan Char pada Pirolisis Rotary Kiln

<p class="00textwithtab">This study aims to investigate the effect of zeolite as a catalyst to enlarge biomass decomposition in the pyrolysis process. It absorbs a high water content in the biomass, besides it makes the easier breaking of biomass molecules to maximize the biomass decomposition into the expected pyrolysis products; tar and char. In addition, to decompose the biomass molecules, the zeolite also stimulates the rate of heat transfer due to its ability to hold and release the heat. If the previous research pyrolysis was conducted in a fixed bed reactor, in this study, it will be carried out rotary kiln as a pyrolysis furnace. If the fixed bed reactor the heat transfer was dominated by conduction, the heat transfer in the rotary kiln is more controlled by the convection and radiation transfer due to stirring and turning of biomass by the kiln. In the study, the biomass used was mahogany with an initial weight of 150 grams. The rotary kiln rotated at 10 rpm and the heating rate during the pyrolysis process was around 0.1483°C/s. The pyrolysis temperatures used were varied as 250°C, 350°C, 450°C. Meanwhile, the percentage of zeolites used from 0% to 60% with a mesh size of 80. The results showed that zeolites were able to increase tar production and maximize the reduction of char as an effect of the Bronsted-Lowry and Lewis reaction in the process of catalytic cracking. The maximum production of tar and char production was also supported by the process of convection and radiation from the rotary kiln wall increasing the rate of heat transfer to decompose the biomass.</p><p class="02abstracttext"> </p>

Efficient Alcoholic Conversion of Glycerol by Engineered Saccharomyces cerevisiae

Glycerol is an eco-friendly solvent that enhances plant biomass decomposition via glycerolysis in many pretreatment methods. Nonetheless, the lack of efficient conversion of glycerol by natural Saccharomyces cerevisiae hinders its use in these methods. Here, we have aimed to develop a complete strategy for the generation of efficient glycerol-converting yeast by modifying the oxidation of cytosolic nicotinamide adenine dinucleotide (NADH) by an O2-dependent dynamic shuttle, while abolishing both glycerol phosphorylation and biosynthesis. By following a vigorous glycerol oxidation pathway, the engineered strain increased the conversion efficiency (CE) to up to 0.49 g ethanol/g glycerol (98% of theoretical CE), with production rate > 1 g×L×h, when glycerol was supplemented in a single fed-batch fermentation in a rich medium. Furthermore, the engineered strain fermented a mixture of glycerol and glucose, producing > 86 g/L bioethanol with 92.8% CE. To our knowledge, this is the highest ever reported titer in this field. Notably, this strategy changed conventional yeast from a non-grower on minimal medium containing glycerol to a fermenting strain with productivity of 0.25-0.5 g×L×h and 84-78% CE, which converted 90% of the substrate to products. Our findings may improve the utilization of glycerol in several eco-friendly biorefinery approaches.

Comprehensive metabolic engineering for fermenting glycerol efficiently in Saccharomyces cerevisiae

ABSTRACTGlycerol is an eco-friendly solvent enhancing plant-biomass decomposition through a glycerolysis process in many pretreatment methods. Nonetheless, the lack of efficient conversion of glycerol by natural Saccharomyces cerevisiae restrains many of these scenarios. Here we outline the complete strategy for the generation of efficient glycerol fermenting yeast by rewriting the oxidation of cytosolic nicotinamide adenine dinucleotide (NADH) by O2-dependent dynamic shuttle while abolishing both glycerol phosphorylation and biosynthesis pathways. By following a vigorous glycerol oxidative pathway, the engineered strain demonstrated augmentation in conversion efficiency (CE) reach up to 0.49g-ethanol/g-glycerol—98% of theoretical conversion—with production rate >1 g/L-1h-1 when supplementing glycerol as a single fed-batch on a rich-medium. Furthermore, the engineered strain showed a new capability toward ferment a mixture of glycerol and glucose with producing >86 g/L of bioethanol with 92.8% of the CE. To our knowledge, this is the highest ever reported titer in this regard. Notably, this strategy flipped our ancestral yeast from non-growth on glycerol, on the minimal medium, to a fermenting strain with productivities 0.25-0.5 g/L-1h-1 and 84-78% of CE, respectively and 90% of total conversions to the products. The findings in metabolic engineering here may release the limitations of utilizing glycerol in several eco-friendly biorefinery approaches.IMPORTANCEWith the avenues for achieving efficient lignocellulosic biorefinery scenarios, glycerol gained keen attention as an eco-friendly biomass-derived solvent for enhancing the dissociation of lignin and cell wall polysaccharides during pretreatment process. Co-fermentation of glycerol with the released sugars from biomass after the glycerolysis expands the resource for ethanol production and release from the burden of component separation. Titer productivities are one of the main obstacles for industrial applications of this process. Therefore, the generation of highly efficient glycerol fermenting yeast significantly promotes the applicability of the integrated biorefineries scenario. Besides, the glycerol is an important carbon resource for producing chemicals. Hence, the metabolic flux control of yeast from glycerol contributes to generation of cell factory producing chemicals from glycerol, promoting the association between biodiesel and bioethanol industries. Thus, this study will shed light on solving the problems of global warming and agricultural wastes, leading to establishment of the sustainable society.

Beach Sand Filtrate as an Alternative Gas Fuel

The golden age of the oil business in Indonesia is over and now petroleum is even a burden. As oil producing countries prepare themselves to start the second phase of the golden era of oil, Indonesia is heading towards an era of energy crisis (Indirasardjana, 2014). Renewable energy is needed as an alternative to meet the community's fuel needs. Beach sand is one material that can be used to help the biomass gasification process. Small particles of sand are filled into a container and gas is flowed from below and suppresses the flow of each particle which is useful for the biomass decomposition process. When using beach sand, we can also utilize heat energy optimally in coastal areas to make gasification reactions easier. This study aims to examine the groups contained in the TMS (Tetramethylsilan) spectrum of the beach sand filtrate fluid by paying attention to the CH3 compounds which are arranged in TMS. FTIR test results show that the beach sand filtrate fluid gives an illustration that from wavelengths of 3000 to 3500 the sharpness of the amount of nitrogen and hydrogen in the sand beach filtrate liquid solution can be used as ammonia gas (a fuel). Nitrogen and Hydrogan when bound with Hydroxide will form ammonium hydroxide which can function as a fuel (heating).

Metabolic engineering of Saccharomyces cerevisiae for efficient conversions of glycerol to ethanol

Glycerol is an eco-friendly solvent enhancing plant-biomass decomposition through the glycell process to bio-based chemicals. Nonetheless, the lack of efficient conversion of glycerol by natural Saccharomyces cerevisiae restrains many biorefineries-scenarios. Here, we outline a comprehensive strategy for generating efficient glycerol fermenting S. cerevisiae via rewriting the oxidation of cytosolic nicotinamide adenine dinucleotide by O2-dependent dynamic shuttle while abolishing glycerol phosphorylation and biosynthesis pathways. By following a vigorous glycerol oxidative pathway, our engineered strain demonstrated a breakthrough in conversion efficiency (CE), reaching up to 0.49g-ethanol/g-glycerol—98% of theoretical conversion—with production rate >1 gL−1h−1 on rich-medium. Interestingly, the glycerol consumption and its fermentation unrepressed during the mixing by glucose until the strain produced >86 g/L of bioethanol with 92.8% of CE. Moreover, fine-tuning of O2 boosted the production rate to >2 gL−1h−1with 82% of CE. Impressively, the strategy flipped the ancestral yeast even from non-growing on glycerol, on the minimal medium, to a fermenting strain with productivities 0.25-0.5 gL−1h−1 and 84-78% of CE, respectively. Our findings promote utlising glycerol efficiently in several eco-friendly biorefinery approaches.SummaryEfficient fermentation of glycerol in S. cerevisiae was established by comprehensive engineering of glycerol pathways and rewriting NADH pathway.

Properties of Thermobifida fusca peroxidase Tfu-1649 and its combined synergistic effects with xylanase on lignocellulose degradation

Lignocelluloses are comprised of cellulose, hemicellulose, and lignins, which constitute plant biomass. Since peroxidases can degrade lignins, the authors examined peroxidase Tfu-1649, which is secreted from the thermophilic actinomycetes, Thermobifida fusca BCRC 19214. After cultivating for 48 h, the culture broth accumulated 43.66 U/mL of peroxidase activity. The treatment of four types of lignocellulolytic byproducts, i.e., bagasse, corncob, pin sawdust, and Zizania latifolia Turcz husk, with Tfu-1649 alone increased the total phenolic compounds, with limited reducing sugars, but treatment with xylanase, Tfu-11, and peroxidase Tfu-1649 showed synergistic effects. Hence, the co-operative degradation of lignocelluloses by both peroxidase and xylanase could contribute to biomass decomposition and further applications in the agricultural and environmental industries.

A Mathematical Model of Biomass Combustion Physical and Chemical Processes

The numerical simulation of biomass combustion requires a model that must contain, on one hand, sub-models for biomass conversion to primary products, which involves calculations for heat transfer, biomass decomposition rate, product fractions, chemical composition, and material properties, and on the other hand, sub-models for volatile products transport inside and outside of the biomass particle, their combustion, and the char reduction/oxidation. Creating such a complete mathematical model is particularly challenging; therefore, the present study proposes a versatile alternative—an originally formulated generalized 3D biomass decomposition model designed to be efficiently integrated with existing CFD technology. The biomass decomposition model provides the chemical composition and mixture fractions of volatile products and char at the cell level, while the heat transfer, species transport, and chemical reaction calculations are to be handled by the CFD software. The combustion model has two separate units: the static modeling that produces a macro function returning source/sink terms and local material properties, and the dynamic modeling that tightly couples the first unit output with the CFD environment independently of the initial biomass composition, using main component fractions as initial data. This article introduces the generalized 3D biomass decomposition model formulation and some aspects related to the CFD framework implementation, while the numerical modeling and testing shall be presented in a second article.