Production Of Second-generation Biofuels Research Articles

Genetic Improvement of Some Trichoderma Isolates for Second-Generation Biofuel Production from Agricultural Wastes.

Genetic Improvement of Some Trichoderma Isolates for Second-Generation Biofuel Production from Agricultural Wastes.

Aquatic plant Nymphaea mexicana as a viable feedstock for second-generation biofuel production

Aquatic plant Nymphaea mexicana as a viable feedstock for second-generation biofuel production

Surfactant-assisted dilute ethylenediamine fractionation of corn stover for technical lignin valorization and biobutanol production

In this study, a surfactant-assisted diluted ethylenediamine (EDA) fractionation process was investigated for co-generation of technical lignin and biobutanol from corn stover. The results showed that the addition of PEG 8000 significantly enhanced cellulose recovery (88.9 %) and lignin removal (68.9 %) in the solid fraction. Moreover, the pulp achieved 86.5 % glucose yield and 82.6 % xylose yield in enzymatic hydrolysis. Structural characterization confirmed that the fractionation process promoted the preservation of active β-O-4 bonds (35.8/100R) in isolated lignin and functionalized the lignin through structural modification using EDA and surfactant grafting. The enzymatic hydrolysate of the pulps yielded a sugar solution for acetone-butanol-ethanol (ABE) fermentation, resulting in an ABE concentration of 15.4 g/L and an overall yield of 137.2 g/Kg of dried corn stalk. Thus, the surfactant-assisted diluted EDA fractionation has the potential to enhance the overall economic feasibility of second-generation biofuels production within the framework of biorefinery.

Production of Industrially Important Cellulases and Pectinases using Lignocellulosic Biomass

Cellulases and pectinases are the two main industrially important enzymes that find significant applications in food, feed, pharmaceutical, textile and environmental sectors. In the present study, Trichoderma asperellum S14 was used for enzymes production in liquid state fermentation and for enzymatic hydrolysis of lignocellulosic biomass. Prior to liquid state fermentation, Trichoderma asperellum S14 was qualitatively screened for the pectinolytic and cellulytic activity by using plate assay method. Alkaline pretreatment (1% NaOH) was used for the pretreatment of lignocellulosic biomasses including; wheat bran, wheat straw, rice straw, rice husk and sugarcane bagasse. Maximum cellulase activity of 4.3 U/mL was observed at pH 4.8 and 30ºC after 72 hours of incubation from Trichoderma asperellum S14 using alkali pretreated sugarcane bagasse as a substrate. While, maximum pectinase activity 9.2 U/mL obtained at pH 4.8 and 30ºC after 72 hours of incubation from Trichoderma asperellum S14 using alkali pretreated wheat bran. Enzymatic hydrolysis was also performed using crude enzymes extract at 50ºC for 72 hours. Maximum hydrolysis (70%) was observed in case of pretreated sugarcane bagasse using Trichoderma asperellum S14 as fungal source for enzyme production. Lignocellulosic biomasses are considered as the best feedstock used in second generation biofuel production because of their renewable resources as well as inexpensive and environment friendly nature. Present study shows the potential of Trichoderma asperellum S14 to degrade variety of lignocellulosic biomass efficiently and could be used to hydrolyze complex lignocellulosic materials towards the production of second generation biofuel.

Synthesis of biodiesel from residual oil extracted from spent bleaching earth using spent bleaching earth-supported catalyst

Proper disposal of spent bleaching earth (SBE) is much anticipated to create a circular economy. In this study, a two-pronged approach was employed to utilise SBE from palm oil refinery for its suitability to act as second-generation biofuel feedstock and catalyst. The SBE was first wet-impregnated and doped with potassium hydroxide (KOH) to further enhance the catalytic activity. The hexane-extracted bleached oil of SBE at conditions of 40 g SBE, 1:4 ratio of oil to n-hexane, and 6 hr extraction time was subjected to different transesterification parameters i.e., catalyst loading, oil: methanol ratio, reaction temperature, and reaction time. The obtained catalysts were characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis, field emission scanning electron microscopy with energy dispersive X-ray, temperature programmed desorption of carbon dioxide (TPD-CO2) and Brunauer-Emmett-Teller (BET) techniques. The N2 adsorption-desorption and TPD-CO2 analyses indicated that SBE/KOH (600 °C) had the highest attainable BET surface area (22.62 m2/g) and basicity (25.82 cm3/g). SBE/KOH (600 °C) exhibited the highest biodiesel yield (80.3%) at the optimised reaction conditions: (80 °C, 2 wt% catalyst loading, 1:20 oil: methanol ratio and 2 h reaction time) compared to 67.3% via the unmodified control. The kinetics study revealed that the experimental results followed the first order reaction kinetics. The activation energy, enthalpy (ΔH) and entropy (ΔS) were determined to be 90.06 kJ/mol, 6.92 × 10−4 kJ/mol and −0.0414 kJ/mol K, respectively while the Gibbs free energy (ΔG) was 15.443 kJ/mol. Overall, SBE has enormous potential as one of the alternative sources for second-generation biofuel production.

Life cycle assessment of a marine biorefinery producing protein, bioactives and polymeric packaging material

Abstract Purpose Algal research has been dominated by the use of marine biomass (mainly microalgae) as feedstock in the production of second-generation biofuels, albeit with limited economic success. A promising alternative strategy is the valorisation of seaweed (macroalgae), with the cascaded extraction of its high-value components, as well as lower-value components further downstream, under the ‘biorefinery concept’. The goal of this study was to assess the environmental performance of one such marine biorefinery situated in the UK. Methods Attributional life cycle assessment (LCA) was conducted on a hypothetical marine biorefinery coproducing fucoidan, laminarin, protein and alginate/cellulose packaging material (target product), from cultivated Saccharina latissima. The functional unit was the production of 1 kg of packaging material. A total of 6 scenarios were modelled, varying in coproduct management methodology (system expansion, mass allocation or economic allocation) and applied energy mix (standard or green energy). Sensitivity analysis was also conducted, evaluating the systems response to changes in allocation methodology; product market value; biomass composition and transport mode and distance. LCA calculations were performed using OpenLCA (version 1.10.3) software, with background processes modelled using the imported Ecoinvent 3.6 database. Environmental impacts were quantified under ReCiPe methodology at the midpoint level, from the ‘Heirarchist’ (H) perspective. Results and discussion The overall global warming impacts ranged from 1.2 to 4.52 kg CO2 eq/kg biopolymer, with the application of economic allocation; 3.58 to 7.06 kg CO2eq/kg with mass allocation and 14.19 to 41.52 kg CO2eq/kg with system expansion — the lower limit representing the instance where green electricity is used and the upper where standard electricity is employed. While implementing the green energy mix resulted in a 67% reduction in global warming impacts, it also incurred a 2–9 fold increase in overall impacts in the categories of terrestrial acidification, human non-carcinogenic toxicity, land-use and terrestrial ecotoxicity. Economic allocation resulted in burden shifting most favourable to the packaging material pathway. Conclusions This study demonstrates that the road to environmental optimisation in marine biorefineries is fraught with trade-offs. From the perspective of LCA — and by extension, the eco-design process that LCA is used to inform — when evaluating such product systems, it serves to strike a balance between performance across a broad spectrum of environmental impact categories, along with having consideration for the nature of energy systems incorporated and LCA methodological elements. Graphical Abstract

Characterization of β-glucosidases from Meridianimaribacter sp. CL38

The production of second-generation biofuel requires a huge amount of freshwater. It is estimated that at least three gal of freshwater is used to produce one gal of biofuel. The replacement of freshwater with seawater serves as a potential alternative in biofuel generation. Therefore, salt-tolerant enzymes play an important role in saccharification and fermentation process. Halophilic β-glucosidase is one of the key enzymes for the process. In this study, the β-glucosidase of halophile Meridianimaribacter sp. CL38 isolated from mangrove soil was characterized. Strain CL38 achieved maximum production of β-glucosidase at 12th hour of growth. The β-glucosidase showed highest activity at 2% (w/v) NaCl while highly stable at salt concentration ranging from 1-2% (w/v) (more than 96% of relative activity). Its β-glucosidase activity remained active in the presence of 5mM Mn2+, Mg2+, Ca2+ ions, and 1% (v/v) Tween-20 and Tween-80. The draft genome sequence of strain CL38 was retrieved from GenBank database and submitted to dbCAN meta server for CAZymes annotation. Strain CL38 harbors 44 GHs and GH3 are annotated as β-glucosidases. The β-glucosidases of Meridianimaribacter flavus (99.61%) and Mesoflavibacter sabulilitoris (97.44%) showed the closest identity with Bgl3a and Bgl3b protein sequences from strain CL38, respectively. Glycoside hydrolase family 3 domain was identified in both enzymes via InterPro scan server. The presence of signal peptides indicated that both enzymes were secreted extracellularly. Five motifs were identified in Bgl3a and Bgl3b, with the active site (nucleophile) found at Asp296 and Asp297, respectively. Collectively, these β-glucosidases could be potentially used in the biofuel production, in particular the lignocellulosic biomass pretreatment process. This is the first attempt to characterize the β-glucosidase in genus Meridianimaribacter as so far none of the lignocellulolytic enzymes from this genus were characterized.

Determination of the Effect of the Addition of Second-Generation Biodiesel BBuE to Diesel Fuel on Selected Parameters of “B” Fuels

Progressive and increasingly noticeable climate change is forcing the search for new energy sources to reduce greenhouse gas emissions, especially carbon dioxide. One way to reduce greenhouse gas emissions is by gradually replacing fossil fuels with biofuels. The authors of this work addressed the production of second-generation biofuel. The purpose of this study was to produce second-generation biodiesel from babassu palm oil (BBuE) and first-generation biodiesel from rapeseed oil (RME), to study their properties, and to determine the effect of the addition of these biodiesels to diesel fuel on selected properties of “B” fuels that affect the fuel–air mixture formation process and the combustion process. Biodiesel from babassu oil was produced because it is non-edible and has a different composition than canola oil. Then, fuels were prepared that were mixtures of diesel oil and biodiesel containing from 10 to 40% (v/v) BBuE or RME (B10, B20, B30, and B40).Tests were conducted on selected physicochemical properties of the obtained fuels. “B” fuels prepared with BBuE and DF were shown to have more favorable fuel properties than those obtained from RME and DF. Fuels that are blends of BBuE and DF have slightly higher heating values, higher cetane number values, a more favorable distillation curve, lower dynamic viscosity values as a function of temperature, and marginally lower flash point values compared to the corresponding blends of RME and DF. Esters with shorter molecules have been shown to have more favorable fuel properties.

Comprehensive Treatment Strategy for Banana Inflorescence Bract to Synthesize Biodiesel and Bioethanol Through Fungal Biorefinery

Banana inflorescence bract (BIB), an agro-waste is sporadically explored for second-generation biofuel production in spite of having considerable holocellulosic composition (cellulose-35.56%, w/w; hemicellulose-22.41%, w/w). In this study, an attempt has been made to utilize this substrate for fermentable sugars (pentose-C5 and hexose-C6) extraction which were employed for the co-production of microbial lipids and ethanol using Rhodosporidium toruloides NCIM 3547 and Saccharomyces cerevisiae respectively. Since, a considerable amount of lignin (8.78%, w/w) is present in BIB, a hybrid pretreatment and carbohydrate hydrolysis through microwave (160 W) assisted mild H2SO4 acid 2.5% (v/v) was adopted. The resultant liquor contains holocellulosic sugars (C5 and C6 sugars), out of which xylose (10.40 ± 0.49 g/L) and glucose (51.48 ± 1.14 g/L). Hence, it was used as the growth medium for R. toruloides to produce lipids i.e., single cell oil (SCO). The maximum lipid content was found to be 44.89 ± 1.25 (%, w/w) containing total saturated fatty acids of 89.07% which justifies its potential application in biodiesel production. On the other hand, the pretreated solid fraction containing cellulose was saccharified using cellulolytic enzyme produced by Aspergillus sp. with saccharification (%) of 69.99 ± 0.30 (%, v/w) and yield of 27.22 ± 0.33 g/L of reducing sugar. This enzymatic hydrolysate was used for ethanol production by Saccharomyces cerevisiae resulting in an ethanol yield of 12.70 ± 0.09 g/L and productivity of 0.132 g/L/h. Based on this outcome, a sustainable route for agro-waste management of BIB was laid by favouring the integrated production of biodiesel and bioethanol towards a biorefinery approach. Exploration and utilization of an agro-waste, banana inflorescence bract is established as a potent feedstock for the co-production of single cell oil and bioethanol is reported for the first time. Microwave-assisted mild acid pretreatment was performed for effective delignification and hydrolysis of holocellulosic components. The resultant liquid hydrolysate consisting of lignin degradatory compounds, pentose (xylose) and hexose (glucose) sugars was used as a growth medium for producing single cell oil, proving its potential application in biodiesel production. Further, the pretreated solid cellulosic fraction was saccharified using crude cellulolytic enzymes and an enzymatic hydrolysate was used for the production of bioethanol through two different fermentative strategies. This study reveals that banana inflorescence bract could act as suitable biomass towards the biorefinery approach. Its complete utilization paved the way for agro-waste management that is not in existence so far according to the authors’ knowledge

The socio-economic impact assessment of biofuels production in South Africa: A rapid structured review of literature

Biofuels as a substitute for conventional aviation and motor vehicle fuels have received considerable global interest over the past decades mainly due to their perceived economic, social, and environmental benefits. Despite these economic benefits, most developing countries, including South Africa (SA), have yet to produce commercial biofuels. This study aims to inform South African policymakers. Prospective producers of biofuels about the potential socio-economic returns from producing biofuels at a commercial level through a structured rapid review of the literature differs from the peer-reviewed studies to date in South Africa, which focussed more on assessing the economic viability and environmental impacts of biofuels production. The systematic review methodology was used. About 48% of the published empirical studies reviewed integrated the socio-economic and environmental impact assessment, followed by studies that only examined the social impacts of biofuel (about 26%), about 15% of the studies examined economic impact only, and 11.54% examined the socio-economic impact. The results revealed that although the production of biofuels is associated with a positive socio-economic benefit, the biofuel industry is not viable without government support and the selling price of biofuel is not competitive relative to gasoline and petroleum alternatives. Lastly, the results revealed a need for more objective empirical studies in South Africa that can quantify the economy-wide implications of biofuels (especially second-generation biofuels) production. Only two (n = 2) of the 28 reviewed studies were conducted in South Africa from 28 studies reviewed. Both studies conducted in South Africa were feasibility studies focusing more on bioethanol; no study quantified the economy-wide impacts. The study recommends the implementation of the biofuels support mechanism by the government. Furthermore, amendments to the existing biofuels regulatory framework are recommended in order to support the production of advanced biofuels.

Biochemical Methane Potential of Mechanically and Enzymatically Pretreated Solid Olive Mill Waste

Olive cake, the solid byproduct of three-phase centrifugation olive oil production, has a high organic and polyphenol content, rendering it an environmental threat when landfilled as well as limiting its animal feed potential. This residue can be a good candidate for biomethane production due to its rich polysaccharide content (pectin, hemicellulose, and cellulose). Two strategies were compared to maximize biomethane production: destoning (i.e., removal of the seed fragments via mechanical means) and enzymatic pretreatment of the pulp. After 30 days of batch anaerobic digestion at 35 °C, both enzymatically pretreated and destoned olive cakes produced similar amounts of methane (~295 mL CH4/g volatile solids (VS)), 42% more than the control. A comparison of olive cake’s biomethane yields with a broad range of agricultural residues in the literature demonstrated its suitability for biomethane production. Additionally, the digestate recovered from the anaerobic digestion of olive cake had high Kjeldahl nitrogen contents (3.6%, db) and low polyphenol concentrations (0.02 mg gallic acid equivalent (GAE)/g), qualifying it as an ingredient for soil amendment. This study demonstrated olive cake can be diverted from landfills for second-generation biofuel production, and that the resulting digestate may have value for soil amendment.

Production of cellulolytic enzymes from microorganisms isolated from coconut fiber

The worldwide production of microbial enzymes is generally limited by the cost of the substrate used for the cultivation of microorganisms. Thinking of a low-cost and abundant lignocellulosic substrate, coconut fiber is an alternative because it is rich in cellulose, hemicellulose, and lignin, presenting itself as a promising raw material for the production of an enzyme cocktail, which can be used in the production of second-generation biofuels. The objective of this work was to produce cellulolytic enzymes from microorganisms isolated from coconut fiber. In the production of the enzyme, the kinetic profile of the enzymatic complex was evaluated, analyzing the effects of moisture content, temperature, and pH during solid-state fermentation of coconut fiber, using a microorganism isolated from the bagasse itself. Statistica software was used to evaluate the enzyme complex production parameters. Statistical results indicated that the best humidity, temperature, and pH conditions were 80%, 30°C and 3, respectively, with activities of 119.93 U/g CMCase (endoglucanase) and 89.32 U/g FPase (total cellulases ) over a period of 48 h.

Microbial Enzyme Systems in the Production of Second Generation Bioethanol

The primary contributor to global warming has been the careless usage of fossil fuels. Urbanization’s threat to the depletion of these resources has made it necessary to find alternatives due to the rising demand. Four different forms of biofuels are now available and constitute a possible replacement for fossil fuels. The first generation of biofuels is generated from the edible portion of biomass, the second generation is made from the non-edible portion of biomass, the third generation is made from algal biomass, and the fourth generation is made using molecular biology to improve the algal strain. Second-generation biofuels are extremely important because they are derived from non-edible biomass, such as agricultural and agro-industrial wastes rich in cellulose, hemicellulose, pectin, and starch impregnated with lignin, and are hydrolyzed after delignification by physio-chemical or biological pretreatments using ligninases. The enzymes involved in the hydrolysis of feedstocks for the production of second-generation bioethanol, a highly acceptable biofuel, are discussed in this article. Furthermore, the article discusses various fermentation technologies as well as significant developments in second-generation biofuel production by combining various microbial enzyme systems.

CeO2-based oxygen storage capacity materials in environmental and energy catalysis for carbon neutrality: extended application and key catalytic properties

ABSTRACT Reducing carbon dioxide emissions is one of the largest energy and environmental challenges currently faced globally. To achieve carbon neutrality, the development of new technologies and simultaneous improvement of conventional technologies are required. Catalysis, which determines the success or failure and efficiency of the process, is at the center of addressing these problems. Innovative advancements in catalysis have been accomplished through the extensive research on catalytic materials. Oxygen storage materials with oxygen storage capacity (OSC) have been widely applied in supports and active cocatalysts for energy and environmental catalytic applications. This review provides knowledge on the extended applications (reforming, water-gas shift reaction, and partial oxidation of methane (POM) for high-value-added chemicals, including hydrogen production, deoxygenation of fatty acids for second-generation biofuel production, selective catalytic reduction of NO x with NH3, hydrocarbon (HCs) oxidation for emission control, CO oxidation for vehicle exhaust control and purification of gaseous product fuel, and soot oxidation for the removal of motor-type pollutants) of these materials, which are mainly used as three-way catalysts (TWC) in automotive catalysis, to the carbon-neutral field. In particular, this study focuses on the physico-chemical properties that are closely synergistic with OSC, such as reducibility, dispersion, surface acid/base properties, and physical properties, such as surface structure or morphology.

Second Generation Bioethanol Production from Soybean Hulls Pretreated with Imidazole as a New Solvent

Soybean hulls (SH) are the main industrial waste from soybean processing, representing 5–8% of the whole grain. Imidazole was employed for the hydrothermal pretreatment of SH and further bioethanol production. Different pretreatment temperatures (120 and 180 °C) and times (1 and 3 h) were tested. Lignin removal and glucose yield were significantly influenced by temperature. After 48 h of enzymatic hydrolysis of imidazole-treated SH (120 °C, 1 h), 32.7 g/L of glucose and 9.4 g/L of xylose were obtained. A maximum bioethanol yield of 78.9% was reached after 12 h of fermentation by Saccharomyces cerevisiae using SH enzymatic hydrolysate. Imidazole appears to be a potential alternative to pretreat lignocellulosic wastes such as SH for the production of second-generation biofuels and other biomolecules.

Phytochemical profiling and biological activity of the extracts obtained from green biomass of three Miscanthus L. species using supercritical carbon dioxide extraction

Taxa belonging to the genus Miscanthus L. (silvergrass) are non-invasive plants that can grow on marginal land that are not suitable for food production. These species give high yields of lignocellulosic biomass, being a rich and renewable source of organic matter for the production of second-generation biofuels (ethanol) and for other practical purposes, such as raw material for paper production. The most promising species of the genus Miscanthus L., in terms of practical use in industry and agriculture, are M. sinensis, M. sacchariflorum and their hydride - M. × giganteus. In this study, extracts obtained from the green biomass of these Miscanthus L. species underwent detailed phytochemical investigation and multidirectional biological evaluation. The extracts were prepared using supercritical fluid extraction with water as co-solvent. The qualitative RP-HPLC/PDA analysis of the extracts after their purification with solid-phase extraction confirmed their similar phytochemical profiles. Six free phenolic acids ( p -hydroxybenzoic, isovanillic, syringic, p -coumaric, ferulic and isoferulic) and one trans -cinnamic acid derivative were identified and determined. The antimicrobial, antiviral, anthelmintic and anticancer activity of the supercritical extracts of Miscanthus L. species studied was revealed for the first time. Moreover, the extracts possessed low cytotoxicity against normal cells. This screening evaluation showed that, besides giving high yields of lignocellulosic biomass, these grasses could also be a source of valuable bioactive compounds for the pharmaceutical and cosmetic industries. • Supercritical carbon dioxide extracts of silvergrasses had similar phenolic profiles. • All slivergrass extracts showed antibacterial and antifungal activities. • Amur and giant silvergrass extracts revealed anthelmintic (nematocidal) effects. • Chinese and giant silvergrass extracts inhibited herpes simplex virus type-1 cycle. • Amur silvergrass extract was selectively cytotoxic against melanoma cells.

Measurement of the critical temperatures, pressures, heat capacities, and thermal diffusivities of four furanic compounds involved in the production of second-generation biofuels

The critical temperatures, critical pressures, heat capacities, and thermal diffusivities have been measured for furfural, furfuryl alcohol, furfuryl acetate, and tetrahydrofurfuryl alcohol, the compounds of industrial importance because they are involved in the production of biofuels. The critical properties have been measured using the pulse-heating method applicable to thermally unstable compounds. The relative combined expanded uncertainties with the 0.95 level of confidence are 0.01 and 0.03 for the critical temperature and pressure of furfural and furfuryl acetate and 0.015 and 0.04 for furfuryl alcohol and tetrahydrofurfuryl alcohol. The acentric factors of the compounds have been calculated based on the experimental data. The critical properties of the compounds have also been calculated by the group contribution methods of Wilson and Jasperson, Nannoolal et al. Marrero and Gani, Hukkerikar et al. in two variants. The Wilson and Jasperson and Nannoolal et al. techniques provide the best estimation of the critical temperature; for the critical pressure, the Nannoolal et al. method gives the best results. The heat capacities in the liquid phase have been measured at atmospheric pressure in the temperature range from 298.15 to 451.15 K by DSC technique with relative combined expanded uncertainty 0.03. The data obtained have been approximated by third-order polynomials. The experimental heat capacities have been compared with those calculated by the group-contribution method of Kolska et al. The thermal diffusivities have been measured by laser flash method at atmospheric pressure in the temperature range from 313.15 to 373.15 K with relative combined expanded uncertainty 0.05. The experimental data have been approximated by first-order polynomials. The thermal conductivities have been calculated using the experimental data obtained.

Constructed wetlands for the removal of pharmaceuticals and personal care products (PPCPs) from wastewater: origin, impacts, treatment methods, and SWOT analysis

The continuous exposure to pharmaceuticals and personal care products can lead to a series of individual antagonistic and synergistic effects and long-lasting toxicity to humans and aquatic lives. This may also lead to developing antibiotic resistance, teratogenic, carcinogenic, and endocrine-disrupting effects. However, several PPCPs are also considered biologically active for non-target aquatic organisms, such as mosquito fish, goldfish, and the algae Pseudokirchneriella subcapitata. Various physicochemical methods such as ozonation, photolysis, and membrane separation are recognized for the effective removal of PPCPs. However, the high operation and maintenance costs and associated ecological impacts have limited their further use. Constructed wetlands are considered eco-friendly and sustainable for the removal of pharmaceuticals and personal care products together with antibiotic resistance genes. Several mechanisms such as sorption, biodegradation, oxidation, photodegradation, volatilization, and hydrolysis are occurring during the phytoremediation of PPCPs. During these processes, more than 50% of PPCPs can be eliminated through constructed wetlands. They also offer several additional benefits as obtained macrophytic biomass may be used as raw material in pulp and paper industries and a source for second-generation biofuel production. In this study, we have discussed the origin and impacts of PPCPs together with their treatment methods. We have also investigated the strengths, weaknesses, opportunities, and threats associated with constructed wetlands during the treatment of wastewater laden with pharmaceutical and personal care products.

Environmental impact of second-generation biofuels production from agricultural residues in Cameroon: A life-cycle assessment study

The world in general, and Cameroon in particular, are facing three major problems which are population increase, natural resource decrease and climate change. This work focuses on assessing the environmental impact of the production of second-generation liquid and gaseous biofuels by means of the life cycle assessment method, in order to contribute to sustainable development with emphasis on environmentally concerned decision-making and appropriate choice of technologies. The increasingly essential Life Cycle Assessment method is at the heart of this work. Avocado, cocoa and peanut residues have been converted on a laboratory scale to second generation gaseous biofuels (biogas) and liquid biofuels (ethanol). Biomethane yields are 177, 127 and 73 mL/g for avocado seed, cocoa pods and peanut shells respectively. When it comes to bioethanol, avocado seed, cocoa pods, and peanut shells produced yields of 178, 61 and 49 mL/kg biomass respectively. Based on the annual production of the three crops, 200,000 kg and 30,376,960 m3 of bioethanol and biomethane respectively can be produced at the national level of Cameroon. The SimaPro software version 9.1.1.1, the Ecoinvent database v.3.6 and the ReCiPe Midpoint impact method v.1.04 were used for the assessment. All categories of resulting environmental impacts are assessed and quantified. The categories with the most significant impacts are land use, global warming, Human non-carcinogenic toxicity, Terrestrial ecotoxicity, Fossil resource scarcity and water consumption observed in the agricultural phase. Global warming, Land use and Terrestrial ecotoxicity are the hot spots observed in the process of converting biomass into bioethanol and biomethane. The main sources of detected impacts are the processes of seed production, the use of electricity, distilled water and chemicals during the process of converting waste to biofuel on a laboratory scale. This laboratory-scale work will serve as a reference for decision-making of pilot plants and then large-scale production of liquid and gaseous biofuels with the objective of promoting the development of a sustainable biomass-energy industry based on avocado seeds, cocoa pods and peanut shells through identification of critical factors.

Thermostabilizing mechanisms of canonical single amino acid substitutions at a GH1 β-glucosidase probed by multiple MD and computational approaches.

β-glucosidases play a pivotal role in second-generation biofuel (2G-biofuel) production. For this application, thermostable enzymes are essential due to the denaturing conditions on the bioreactors. Random amino acid substitutions have originated new thermostable β-glucosidases, but without a clear understanding of their molecular mechanisms. Here, we probe by different molecular dynamics simulation approaches with distinct force fields and submitting the results to various computational analyses, the molecular bases of the thermostabilization of the Paenibacillus polymyxa GH1 β-glucosidase by two-point mutations E96K (TR1) and M416I (TR2). Equilibrium molecular dynamic simulations (eMD) at different temperatures, principal component analysis (PCA), virtual docking, metadynamics (MetaDy), accelerated molecular dynamics (aMD), Poisson-Boltzmann surface analysis, grid inhomogeneous solvation theory and colony method estimation of conformational entropy allow to converge to the idea that the stabilization carried by both substitutions depend on different contributions of three classic mechanisms: (i) electrostatic surface stabilization; (ii) efficient isolation of the hydrophobic core from the solvent, with energetic advantages at the solvation cap; (iii) higher distribution of the protein dynamics at the mobile active site loops than at the protein core, with functional and entropic advantages. Mechanisms i and ii predominate for TR1, while in TR2, mechanism iii is dominant. Loop A integrity and loops A, C, D, and E dynamics play critical roles in such mechanisms. Comparison of the dynamic and topological changes observed between the thermostable mutants and the wildtype protein with amino acid co-evolutive networks and thermostabilizing hotspots from the literature allow inferring that the mechanisms here recovered can be related to the thermostability obtained by different substitutions along the whole family GH1. We hope the results and insights discussed here can be helpful for future rational approaches to the engineering of optimized β-glucosidases for 2G-biofuel production for industry, biotechnology, and science.