Addition Of Substrate Research Articles

Microbial Fuel Cell Based on Nitrogen-Fixing Rhizobium anhuiense Bacteria.

In this study, the nitrogen-fixing, Gram-negative soil bacteria Rhizobium anhuiense was successfully utilized as the main biocatalyst in a bacteria-based microbial fuel cell (MFC) device. This research investigates the double-chambered, H-type R. anhuiense-based MFC that was operated in modified Norris medium (pH = 7) under ambient conditions using potassium ferricyanide as an electron acceptor in the cathodic compartment. The designed MFC exhibited an open-circuit voltage (OCV) of 635 mV and a power output of 1.07 mW m−2 with its maximum power registered at 245 mV. These values were further enhanced by re-feeding the anode bath with 25 mM glucose, which has been utilized herein as the main carbon source. This substrate addition led to better performance of the constructed MFC with a power output of 2.59 mW m−2 estimated at an operating voltage of 281 mV. The R. anhuiense-based MFC was further developed by improving the charge transfer through the bacterial cell membrane by applying 2-methyl-1,4-naphthoquinone (menadione, MD) as a soluble redox mediator. The MD-mediated MFC device showed better performance, resulting in a slightly higher OCV value of 683 mV and an almost five-fold increase in power density to 4.93 mW cm−2. The influence of different concentrations of MD on the viability of R. anhuiense bacteria was investigated by estimating the optical density at 600 nm (OD600) and comparing the obtained results with the control aliquot. The results show that lower concentrations of MD, ranging from 1 to 10 μM, can be successfully used in an anode compartment in which R. anhuiense bacteria cells remain viable and act as a main biocatalyst for MFC applications.

Declining carbohydrate solubilization with increasing solids loading during fermentation of cellulosic feedstocks by Clostridium thermocellum: documentation\xa0and diagnostic tests

BackgroundFor economically viable 2nd generation biofuels, processing of high solid lignocellulosic substrate concentrations is a necessity. The cellulolytic thermophilic anaerobe Clostridium thermocellum is one of the most effective biocatalysts for solubilization of carbohydrate harbored in lignocellulose. This study aims to document the solubilization performance of Clostridium thermocellum at increasing solids concentrations for two lignocellulosic feedstocks, corn stover and switchgrass, and explore potential effectors of solubilization performance.ResultsMonocultures of Clostridium thermocellum demonstrated high levels of carbohydrate solubilization for both unpretreated corn stover and switchgrass. However, fractional carbohydrate solubilization decreases with increasing solid loadings. Fermentation of model insoluble substrate (cellulose) in the presence of high solids lignocellulosic spent broth is temporarily affected but not model soluble substrate (cellobiose) fermentations. Mid-fermentation addition of cells (C. thermocellum) or model substrates did not significantly enhance overall corn stover solubilization loaded at 80 g/L, however cultures utilized the model substrates in the presence of high concentrations of corn stover. An increase in corn stover solubilization was observed when water was added, effectively diluting the solids concentration mid-fermentation. Introduction of a hemicellulose-utilizing coculture partner, Thermoanaerobacterium thermosaccharolyticum, increased the fractional carbohydrate solubilization at both high and low solid loadings. Residual solubilized carbohydrates diminished significantly in the presence of T. thermosaccharolyticum compared to monocultures of C. thermocellum, yet a small fraction of solubilized oligosaccharides of both C5 and C6 sugars remained unutilized.ConclusionDiminishing fractional carbohydrate solubilization with increasing substrate loading was observed for C. thermocellum-mediated solubilization and fermentation of unpretreated lignocellulose feedstocks. Results of experiments involving spent broth addition do not support a major role for inhibitors present in the liquid phase. Mid-fermentation addition experiments confirm that C. thermocellum and its enzymes remain capable of converting model substrates during the middle of high solids lignocellulose fermentation. An increase in fractional carbohydrate solubilization was made possible by (1) mid-fermentation solid loading dilutions and (2) coculturing C. thermocellum with T. thermosaccharolyticum, which ferments solubilized hemicellulose. Incomplete utilization of solubilized carbohydrates suggests that a small fraction of the carbohydrates is unaffected by the extracellular carbohydrate-active enzymes present in the culture.

The Lipid Droplet Knowledge Portal: A resource for systematic analyses of lipid droplet biology.

Lipid droplets (LDs) are organelles of cellular lipid storage with fundamental roles in energy metabolism and cell membrane homeostasis. There has been an explosion of research into the biology of LDs, in part due to their relevance in diseases of lipid storage, such as atherosclerosis, obesity, type 2 diabetes, and hepatic steatosis. Consequently, there is an increasing need for a resource that combines datasets from systematic analyses of LD biology. Here, we integrate high-confidence, systematically generated human, mouse, and fly data from studies on LDs in the framework of an online platform named the "Lipid Droplet Knowledge Portal" (https://lipiddroplet.org/). This scalable and interactive portal includes comprehensive datasets, across a variety of cell types, for LD biology, including transcriptional profiles of induced lipid storage, organellar proteomics, genome-wide screen phenotypes, and ties to human genetics. This resource is a powerful platform that can be utilized to identify determinants of lipid storage.

Unravelling biogeochemical drivers of methylmercury production in an Arctic fen soil and a bog soil

Arctic tundra soils store a globally significant amount of mercury (Hg), which could be transformed to the neurotoxic methylmercury (MeHg) upon warming and thus poses serious threats to the Arctic ecosystem. However, our knowledge of the biogeochemical drivers of MeHg production is limited in these soils. Using substrate addition (acetate and sulfate) and selective microbial inhibition approaches, we investigated the geochemical drivers and dominant microbial methylators in 60-day microcosm incubations with two tundra soils: a circumneutral fen soil and an acidic bog soil, collected near Nome, Alaska, United States. Results showed that increasing acetate concentration had negligible influences on MeHg production in both soils. However, inhibition of sulfate-reducing bacteria (SRB) completely stalled MeHg production in the fen soil in the first 15 days, whereas addition of sulfate in the low-sulfate bog soil increased MeHg production by 5-fold, suggesting prominent roles of SRB in Hg(II) methylation. Without the addition of sulfate in the bog soil or when sulfate was depleted in the fen soil (after 15 days), both SRB and methanogens contributed to MeHg production. Analysis of microbial community composition confirmed the presence of several phyla known to harbor microorganisms associated with Hg(II) methylation in the soils. The observations suggest that SRB and methanogens were mainly responsible for Hg(II) methylation in these tundra soils, although their relative contributions depended on the availability of sulfate and possibly syntrophic metabolisms between SRB and methanogens.

Initial growth and production of secondary metabolites in Basella alba leaves cultivated in a sandy textured soil with addition of organic and organo-mineral substrate

La especie Basella alba se conoce popularmente como bertalha india y se consume ampliamente en forma de ensaladas, por ejemplo. El objetivo de este estudio fue evaluar las etapas iniciales de crecimiento y la producción de metabolitos secundarios en diferentes sustratos. Transcurridos 90 días desde el inicio de la plantación (pleno sol), en suelo arenoso mezclado con diferentes sustratos, se determinó el efecto de los sustratos sobre el crecimiento y producción de metabolitos secundarios en las hojas. Los resultados indicaron que el tratamiento con la adición de 70% de vermicompost indujo el mayor crecimiento y la mejor concentración de compuestos fenólicos y flavonoides. Sin embargo, la mayoría de los tratamientos dieron como resultado la producción de heterósidos cardiotónicos, que pueden causar problemas de salud. The species Basella alba is popularly known as Indian bertalha and is widely consumed in the form of salads, for example. Due to its potential for use, the objective of this study was to evaluate the initial stages of growth and the production of secondary metabolites in different substrates. After 90 days from the beginning of planting (full sun), in sandy soil mixed with different substrates, the effect of substrates on growth and the production of secondary metabolites in leaves was determined. The results indicated that the treatment with the addition of 70% of vermicompost induced the highest growth and the best concentration of phenolic and flavonoid compounds. However, most of the treatments resulted in the production of cardiotonic heterosides, which can cause health problems.

The Influence of Transglutaminase on Minced Muscular Fish Tissue Structure Formation After the Application of Various Protein Substrates

This research aimed to examine the effect of a microbial transglutaminase preparation (Activa® GS, Ajinomoto Co., Inc, Japan) on the structure formation of the myofibrillar protein system of a deep-sea fish species – the giant grenadier – after the addition of various protein substrates. The low content of proteins and their low water-holding capacity in this fish, subjected to various processing methods, leads to significant losses in the initial mass and decreased gelation ability in the muscle tissue system. Various concentrations of transglutaminase were used but these did not ensure the restructuring of the initial muscle tissue of the grenadier. Additional protein substrates with different molecular weights and amino acid composition were added, including gelatin, milk casein, hydrolysates of the skin and milt of the fish, and whole bivalves, which were used to create a firm structure. It was shown that the introduction of gelatin and casein at a concentration of 5% led to the formation of a firm, thermostable structure under the action of the enzyme, while hydrolyzed proteins with low molecular weight at their various concentrations enhanced the expression of water and formation of the fluid consistency. The ability of gastrointestinal tract proteases (pepsin and trypsin) to digest did not depend on the formation of protein-to-protein cross-linking in these combined products. The influence on the growth of the Tetrahymena pyriformis ciliates test culture also showed the high degree of product availability. The technology of molded products based on fermented minced muscle tissue of grenadier with added casein, both in the form of semi-finished products and in the form of ready-to-eat products, was developed.
 Keywords: transglutaminase, muscle tissue, structure formation, deep-sea fish

Biogas Generation from Maize and Cocksfoot Growing in Degraded Soil Enriched with New Zeolite Substrate

Degraded lands are potential areas for obtaining biomass which can serve as an energy source after its conversion into biogas. Thus, the studies on biogas production from maize and cocksfoot biomasses obtained from degraded soil supplemented with additions of new zeolite substrate (Z-ion as the nutrient carrier) and on arable soil (reference soil) were carried out during batch digestion tests. It was found that the biogas and biomethane potentials and specific energy of the test species growing in degraded soil enriched with Z-ion additions (1% and 5% v/v in the cases of cocksfoot and maize, respectively) did not differ significantly from the values of these parameters that were found for the plants growing in arable soil. The application of Z-ion to the degraded soil (especially in a dose of 5% v/v) resulted in an increase in the nitrogen content and decrease (below the lower optimum value) in the C/N ratio in the plant biomass. However, these changes did not negatively influence the final values of the biogas or methane potentials or the specific energy found for the maize biomass. Therefore, the study results indicated the usefulness of Z-ion substrate for improving the growth conditions for energy crops in degraded soils and, as a consequence, obtaining a plant feedstock suitable for the digestion process.

Multiplex Hextuple Luciferase Assaying.

We recently expanded the commonly used dual luciferase assaying method toward multiplex hextuple luciferase assaying, allowing monitoring the activity of five experimental pathways against one control at the same time. In doing so, while our expanded assay utilizes a total of six orthogonal luciferases instead of two, this assay, conveniently, still utilizes the well-established reagents and principles of the widely used dual luciferase assay. Three quenchable D-luciferin-consuming luciferases are measured after addition of D-Luciferin substrate, followed by quenching of their bioluminescence (BL) and the measurement of three coelenterazine (CTZ)-consuming luciferases after addition of CTZ substrate, all in the same vessel. Here, we provide detailed protocols on how to perform such multiplex hextuple luciferase assaying to monitor cellular signal processing upstream of five transcription factors and their corresponding transcription factor-binding motifs, using a constitutive promoter as normalization control. The first protocol is provided on how to perform cell culture in preparation toward genetic or pharmaceutical perturbations, as well as transfecting a multiplex hextuple luciferase reporter vector encoding all luciferase reporter units needed for multiplex hextuple luciferase assaying. The second protocol details on how to execute multiplex hextuple luciferase assaying using a microplate reader appropriately equipped to detect the different BLs emitted by all six luciferases. Finally, the third protocol provides details on analyzing, plotting, and interpreting the data obtained by the microplate reader.

Sustainable technology for modern era effluent treatment: Microbial fuel cell

Wastewater generated from allied industry contains high organic load and the treatment is primary carried out using biological methods. Sustainable wastewater treatment is considered the most advanced and cost-effective solution for the high organically polluted industrial waste stream. However normal treatment plants are associated with the recovery of energy that seems to be a potential approach for waste treatment and conservation. On the other hand, Microbial Fuel Cell (MFC) represent a new bio-electrochemical system for generation of electricity directly from biodegradable organic compound. This enables us to harness the power of organic compounds through the action of microbes. In the current scenario, Industrial wastewater is a potential hazard to the natural water body. The waste water contains many organic matter, which is toxic to the various life forms of the system. Industrial waste water has a complex mixture of chemicals whose behaviour alter towards biological systems. Treatment of waste water is therefore over riding process. This study is designed to treat waste water with the generation of bioelectricity and minimising the parameter of the waste water before it been released into a water source. Primary treatment of waste water is done with the help of corn cobbed to eliminate primary treatment of wastewater and the addition of substrate in the MFC. In the current study efficiency of Microbial Fuel Cell (MFC) in eliminating contaminate and generation of bioelectricity was determined, its break-even point was analysed and 15 L model was constructed for the operational analysis and to put into effect on a large industrial scale. From the experiment, we found that MFC is an effective method for waste water treatment with the generation of bio-electricity.

Effect of Molasses Concentration on the Pigment Production of Monascus purpureus M9 on Monascus Fermented Durian Seed

Efforts have been made to cultivate Monascus purpureus on durian seed to produce Monascus Fermented Durian Seed (MFDS). MFDS pigment production could be enhanched by substrate addition by adding carbon source such as molasses. The purpose of this study was to determine the effect of molasses concentration on the production of M.purpureus M9 pigment in MFDS. The research used randomized block design with one factor, namely the concentration of molasses (M) with six treatment levels, M0 = 0%; M1 = 2%; M2 = 4%; M3= 6%; M4 = 8% and M5 = 10% with four repetitions. Findings showed that molasses addition had a significant effect on the color of MFDS powder, water soluble pigment level, 99.9% ethanol soluble pigment level and the pigment profile for both solvents. The best treatment based on pigment content was the M4 treatment with an ‘L value’ of 43.83, a* value of 14.92, b* value of 7.08, C value of 16.54, oH value of 24.45 and aquades soluble pigment content of 16.86AU/g (yellow); 9.23AU/g (orange); and 8.19AU/g (red) and ethanol soluble pigment content of 9.8AU/g (yellow); 2.5AU/g (orange); and 3.0 AU/g (red). Molasses is able to enhance pigment production of Monascus purpureus M9 of MFDS.

Addition of a Carbon-Rich Substrate to a Constructed Wetland Favours Carbon and Phosphorus Availability and Biota Development: Relevance for Treating Agricultural Water

Addition of a Carbon-Rich Substrate to a Constructed Wetland Favours Carbon and Phosphorus Availability and Biota Development: Relevance for Treating Agricultural Water

Bioremediasi air asam tambang batubara dengan pengayaan bakteri pereduksi sulfat dan penambahan substrat organik

Acid mine drainage (AMD) has a negative impact that must be managed because it can cause environmental pollution and disrupt mining operations. Acid mine drainage contains dissolved heavy metals that are harmful to the ecosystem. Sulfate-reducing bacteria (SRB) can be used in acid mine drainage bioremediation. This study aims to analyze pH, C-organic and BPS growing in acid water sediments of coal mines and several other ecosystems, analyze C/N ratio and pH of potential organic substrates, and recover AMD by enrichment of indigenous SRB and addition of organic substrates. The ecosystems observed were AMD sediment, paddy field mud, mangrove sediment, in situ sediment, ditch sediment, and rhizosphere soil. The organic materials tested included water hyacinth compost, a mixture of paddy field mud with wood sawdust, oil palm empty fruit bunch (EFB) compost, chicken manure, cow manure, dairy factory waste, and mixtures thereof. The results showed that SRB could be found in all studied ecosystems in the range of 5.8E+2 – 1.26E+5 MPN-unit/dry weight. The value of the C/N ratio with variations from 9.23-89.5 had a negative correlation with increasing pH. The application of organic matter with concentrations of 3%, 5%, 7%, and 10% helped SRB to raise the pH of AMD to more than 6 and reduced Fe by 88.18 – 97.27%. The highest SRB population was obtained in the mixed treatment of EFB and chicken manure with a population of 2.41E+12 MPN- unit/dry weight.

Imaging of Autonomous Bioluminescence Emission From Single Mammalian Cells.

The bioluminescent visualization of individual mammalian cells usually requires the addition of a luciferin substrate. This chapter describes the microscopic imaging of single cells by their bioluminescence (BL) emission generated without an external luciferin. Imaging is based on the expression of codon-optimized lux (co lux) genes and does not require manipulation of the cells apart from transfection. Due to the high brightness of the co lux system, light emission from single cells can be observed continuously for many hours using a specialized microscope.

CO2 sensing performance enhanced by Pt-catalyzed SnO2/porous-silicon hybrid structures

In this work, pristine and Pt-catalyzed SnO2 hybrid structures were designed over porous Si (p-Si) substrates via chemical bath deposition. CO2 gas sensing properties such as sensing response, response/ recovery time were studied as a function of different platinum concentrations and compared with the devices prepared over c-Si substrates. TEM analysis confirms the nanometric size of ∼2.5 ​nm of the Pt nanoparticles. XRD analysis for the hybrid nanostructures confirms the presence of tetragonal structure of SnO2. SEM and EDS analysis of the SnO2 nanostructures confirms the spherical morphology and the composition respectively. Significant sensing response of hybrid nanostructures could be obtained at low operating temperature (∼100 ​°C). At an optimal concentration of PtNPs, the sensitivity of pSi based hybrid structures increased by a factor of ∼7.5 compared to the ones on crystalline-Si. The higher sensitivity is possibly due to the charge carrier exchange enhancement in the Pt–SnO2 interface in addition to the high surface area provided by p-Si. The increment in the p-Si surface area also led to the higher population of active sites and the charge transfer leads to a more efficient dissociation of adsorbed H2O molecules, which further served as active sites for CO2 detection. The CO2 gas sensing mechanism with respect to different substrate and Pt addition is explained in terms of adsorbed OH− ions reacting with CO2 molecules at the SnO2 surface. The utilization of the proposed hybrid structures with high surface area favors the miniaturization of possible device fabrication for real-life applications.

Computational study of the boraformylation of allenes catalyzed by copper complexes

The bifunctionalization of allenes is a powerful tool with potential for generating many pharmaceuticals, natural products, and biologically active molecules. In this study, theoretical calculations based on the density functional theory (DFT) were used to investigate the mechanism involved in the boraformylation of propadiene catalyzed by an active copper complex bearing a bulky phosphine group as an ancillary ligand. The process was characterized by a four-step mechanism, in which the transition state with the highest energy is that one associated with the substrate addition to the active catalyst, while the largest energy barrier is found to the β-elimination step. In addition, the non-covalent interaction (NCI) analysis performed over all the transition states unveiled the importance of non-covalent interactions to the entire reaction mechanism.

Effects of Temperature on the Activity of Congregibacter litoralis KT 71 β -lactamase in the Hydrolysis of 4-nitrophenyl Dodecanoate

The effects of temperature on the activities of Congregibacter litoralis KT71 β-lactamase (CLL) was determined by varying the assay temperature from 30°C to 70°C. The enzyme’s residual activity was also determined by incubating the assay mixture which excluded the substrate for one hour at 70°C before addition of the substrate to start the reaction. The enzyme activity was measured using a spectrophotometer at a wavelength of 405 nm. The hydrolysis of 4-nitrophenyl dodecanoate to yield 4-nitrophenol was monitored by reading the absorbance at 25 minutes after the addition of substrate to the pre incubated assay mixture. The assay was done in three replicates. The initial velocity was determined and this was compared with Thermomyces lanuginosus Lipase (TLL) which served as a reference enzyme. Results show that increase in temperature from 30°C to 70°C proportionately decreased the activity of Congregibacter litoralis KT71 β-lactamase. Similarly, Thermomyces Lanuginosus Lipase showed a progressively decreasing activity as the temperature increased within the same range. Results from the assay on the residual activity at 70°C shows that both CLL and TLL has residual activities of 63% and 48% respectively. This suggests that reactions involving these enzymes at 70°C can occur without the enzyme completely inactivated. Results also shows that CLL is more thermally stable than TLL at 70°C. Considering the vast importance of thermally stable lipases and their industrial applications, there is need to study the kinetics of this enzyme to give an understanding of how the enzyme system works. Hence findings from this study is of great significance.

Priming effect and its regulating factors for fast and slow soil organic carbon pools: A meta-analysis

The priming effect (PE) plays a critical role in the control of soil carbon (C) cycling and influences the alteration of soil organic C (SOC) decomposition by fresh C input. However, drivers of PE for the fast and slow SOC pools remain unclear because of the varying results from individual studies. Using meta-analysis in combination with boosted regression tree (BRT) analysis, we evaluated the relative contribution of multiple drivers of PE with substrate and their patterns across each driver gradient. The results showed that the variability of PE was larger for the fast SOC pool than for the slow SOC pool. Based on the BRT analysis, 67% and 34% of the variation in PE were explained for the fast and slow SOC pools, respectively. There were seven determinants of PE for the fast SOC pool, with soil total nitrogen (N) content being the most important, followed by, in a descending order, substrate C:N ratio, soil moisture, soil clay content, soil pH, substrate addition rate, and SOC content. The directions of PE were negative when soil total N content and substrate C:N ratio were below 2 g kg -1 and 20, respectively, but the directions changed from negative to positive with increasing levels of this two factors. Soils with optimal water content (50%–70% of the water-holding capacity) or moderately low pH (5–6) were prone to producing a greater PE. For the slow SOC pool, soil pH and soil total N content substantially explained the variation in PE. The magnitude of PE was likely to decrease with increasing soil pH for the slow SOC pool. In addition, the magnitude of PE slightly fluctuated with soil N content for the slow SOC pool. Overall, this meta-analysis provided new insights into the distinctive PEs for different SOC pools and indicated knowledge gaps between PE and its regulating factors for the slow SOC pool.

Temperature sensitivity of organic matter mineralization as affected by soil edaphic properties and substrate quality

Warming in ecosystems simultaneously changes soil temperatures and inputs of organic matter into soils. Soil chemical properties and exogenous substrate inputs both have significant effects on the temperature sensitivity (Q10) of mineralization. In this study, three soil types (Cambisol, Chernozem and Luvisol) were collected from natural forests at three latitudes in temperate China, whereas the vegetation types are mixed broadleaf-conifer, broadleaf and conifer respectively. The soils differed in soil organic carbon (SOC) contents in the order Chernozem (8.5%), Luvisol (6%), Cambisol (3.6%). The soils were incubated for 40 days at three temperatures (5, 15, and 25 °C). Glucose and maize leaf powder were added as exogenous substrates. To add the same amounts of soluble carbon glucose and maize leaf powder were added at the rate of 2 and 4 mg C g−1 soil, respectively. Independent of substrate addition, the Chernozem had the highest cumulative CO2 efflux under all temperature treatments. Maize addition accelerated cumulative CO2 efflux more than glucose in most treatments. The Q10 value was higher (P < 0.05) in the Chernozem (1.29 ∼ 1.49) than the Cambisol (1.17 ∼ 1.28) and the Luvisol (1.10 ∼ 1.29), both in the treatments and the control. Soil Q10 was positively correlated (P < 0.001) with DOC and mineral N content, but negatively correlated (P < 0.001) with the MBC/MBN ratio. However, the effect of exogenous substrate addition on Q10 varied between the different soil types. Addition of both substrates reduced Q10 by 8.7 ∼ 13.4% in the Chernozem and by 10 ∼ 14.0% in the Luvisol, whereas maize input increased (P < 0.05) Q10 by 7.6% in the Cambisol. These results suggested that DOC, mineral N and MBC/MBN ratio significantly influenced Q10, whereas the effects of exogenous substrates on soil respiration and Q10 were highly dependent on SOC content and substrate type.

Warming and Labile Substrate Addition Alter Enzyme Activities and Composition of Soil Organic Carbon

Warming can increase the efflux of carbon dioxide (CO2) from soils and can potentially feedback to climate change. In addition to warming, the input of labile carbon can enhance the microbial activity by stimulating the co-metabolism of recalcitrant soil organic matter (SOM). This is particularly true with SOM under invaded ecosystems where elevated CO2and warming may increase the biomass of invasive species resulting in higher addition of labile substrates. We hypothesized that the input of labile carbon would instigate a greater soil organic carbon (SOC) loss with warming compared to the ambient temperature. We investigated this by incubating soils collected from a native pine (Pinus taeda) forest to which labile carbon from the invasive species kudzu (Pueraria lobata) was added. We evaluated the microbial extracellular enzyme activity, molecular composition of SOC and the temperature sensitivity of soil CO2efflux under warming and labile carbon addition. After 14 months of soil incubation, the addition of labile C through kudzu extract increased the activity of β-1,4-glucosidase compared with the control. However, the activity of N-acetyl-β-D-glucosaminidase and fungal biomass (ergosterol) decreased with labile carbon addition. The activity of peroxidase increased with warming after 14 months of soil incubation. Although the carbon content of incubated soils did not vary with substrate and temperature treatments, the molecular composition of SOC indicated a general decrease in biopolymers such as cutin, suberin, long-chain fatty acids, and phytosterol with warming and an increasing trend of microbial-derived compounds with labile substrate addition. In soils that received an addition of labile C, the macro-aggregate stability was higher while the temperature sensitivity of soil C efflux was lower compared with the control. The increase in aggregate stability could enhance the physical protection of SOC from microbial decomposition potentially contributing to the observed pattern of temperature sensitivity. Our results suggest that warming could preferentially accelerate the decomposition of recalcitrant compounds while the addition of labile substrates could enhance microbial-derived compounds that are relatively resistant to further decomposition. Our study further emphasizes that global change factors such as plant invasion and climate change can differentially alter soil microbial activity and the composition of SOC.

Bioethanol from Napier grass employing different fermentation strategies to evaluate a suitable operation for batch bioethanol production

• Variations in substrate and enzyme additions in SSF of Napier grass were compared. • SHF and SSF resulted in 30.6 g/L and 28.5 g/L ethanol from 15% Napier grass. • Alleviate mixing problem by portioning addition did not improve ethanol production. • Pre-incubating the grass before SSF negatively impacts ethanol production. • Extra loading of substrate during SSF resulted in higher ethanol production. Napier grass has been used as animal feed especially in countries with tropical climates. As interest in alternative feedstocks for fuel bioethanol increases, Napier grass has been considered as a potential feedstock for lignocellulosic bioethanol production. Two main fermentation strategies, including separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF), were investigated with various substrate and enzyme feeding patterns in SSF. Total substrate loading of 15% and enzyme dosage of 40 FPU/g substrate were controlled to compare the performance of each fermentation variation. SHF and SSF resulted in similar ethanol production of 30.6 ± 0.4 g/L and 28.5 ± 2.3 g/L. Preincubation of grass and enzyme resulted in significant lower ethanol at 20.3 ± 1.6 g/L. Portioning the addition of grass and enzyme did not change the ethanol production significantly. Increasing the grass loading to 30% via portioning approach resulted in an increase in ethanol production in batch fermentation, while the addition of extra enzyme did not help with increasing ethanol production.