Source Of Lignocellulosic Biomass Research Articles

Mechanism of Zn2+ regulation of cellulase production in Trichoderma reesei Rut-C30

BackgroundTrichoderma reesei Rut-C30 is a hypercellulolytic mutant strain that degrades abundant sources of lignocellulosic plant biomass, yielding renewable biofuels. Although Zn2+ is an activator of enzymes in almost all organisms, its effects on cellulase activity in T. reesei have yet to be reported.ResultsAlthough high concentrations of Zn2+ severely suppressed the extension of T. reesei mycelia, the application of 1–4 mM Zn2+ enhanced cellulase and xylanase production in the high-yielding cellulase-producing Rut-C30 strain of T. reesei. Expression of the major cellulase, xylanase, and two essential transcription activator genes (xyr1 and ace3) increased in response to Zn2+ stimulation. Transcriptome analysis revealed that the mRNA levels of plc-e encoding phospholipase C, which is involved in the calcium signaling pathway, were enhanced by Zn2+ application. The disruption of plc-e abolished the cellulase-positive influence of Zn2+ in the early phase of induction, indicating that plc-e is involved in Zn2+-induced cellulase production. Furthermore, treatment with LaCl3 (a plasma membrane Ca2+ channel blocker) and deletion of crz1 (calcineurin-responsive zinc finger transcription factor 1) indicated that calcium signaling is partially involved in this process. Moreover, we identified the zinc-responsive transcription factor zafA, the transcriptional levels of which declined in response to Zn2+ stress. Deletion of zafA indicates that this factor plays a prominent role in mediating the Zn2+-induced excessive production of cellulase.ConclusionsFor the first time, we have demonstrated that Zn2+ is toxic to T. reesei, although promotes a marked increase in cellulase production. This positive influence of Zn2+ is facilitated by the plc-e gene and zafA transcription factor. These findings provide insights into the role of Zn2+ in T. reesei and the mechanisms underlying signal transduction in cellulase synthesis.

Challenges in Syngas Fermentation for Bioethanol Production: Syngas Composition

Energy challenges in developing countries are more significant if they continue to use fossil materials and have an impact on air quality. Lignocellulosic biomass can be an alternative to new renewable sources to replace fossil materials. Indonesia produces various sources of lignocellulosic biomass, which can be used in multiple energy sources such as bioethanol. The hybrid pathway is one of the routes for producing bioethanol. The first stage of the hybrid process is the conversion of biomass into CO, CO2, and H2 (syngas) gas through the gasification process. Then the syngas is converted into bioethanol through fermentation using microorganisms as biocatalysts. The bioethanol production line is the Wood-Ljungdahlii pathway. Factors that affect syngas are the type of biomass (chemical, physical, and morphological properties) and the gasification process (type of gasifier, temperature, gasification agent, and ratio equilibrium (ER)). This paper reviews the challenges in implementing syngas fermentation. In particular, variations in the composition of syngas as a substrate for fermentation.

From trash to treasure: Sourcing high-value, sustainable cellulosic materials from living bioreactor waste streams

The appreciation of how conventional and fossil-based materials could be harmful to our planet is growing, especially when considering single-use and non-biodegradable plastics manufactured from fossil fuels. Accordingly, tackling climate change and plastic waste pollution entails a more responsible approach to sourcing raw materials and the adoption of less destructive end-of-life pathways. Livestock animals, in particular ruminants, process plant matter using a suite of mechanical, chemical and biological mechanisms through the act of digestion. The manure from these “living bioreactors” is ubiquitous and offers a largely untapped source of lignocellulosic biomass for the development of bio-based and biodegradable materials. In this review, we assess recent studies made into manure-based cellulose materials in terms of their material characteristics and implications for sustainability. Despite the surprisingly diverse body of research, it is apparent that progress towards the commercialisation of manure-derived cellulose materials is hindered by a lack of truly sustainable options and robust data to assess the performance against conventional materials alternatives. Nanocellulose, a natural biopolymer, has been successfully produced by living bioreactors and is presented as a candidate for future developments. Life cycle assessments from non-wood sources are however minimal, but there are some initial indications that manure-derived nanocellulose would offer environmental benefits over traditional wood-derived sources.

High-pressure microwave-assisted pretreatment of softwood, hardwood and non-wood biomass using different solvents in the production of cellulosic ethanol

BackgroundPretreatment is an indispensable stage of the preparation of lignocellulosic biomass with key significance for the effectiveness of hydrolysis and the efficiency of the production of cellulosic ethanol. A significant increase in the susceptibility of the raw material to further degradation can be attained as a result of effective delignification in high-pressure conditions. With this in mind, a method of high-pressure pretreatment using microwave radiation and various solvents (water, 40% w/v NaCS, 1% v/v H2SO4, 1% w/v NaOH or 60% v/v EtOH with an addition of 1% v/v H2SO4) was developed, enabling the acquisition of biomass with an increased susceptibility to the process of enzymatic hydrolysis. The medium obtained in this way can be used for the production of cellulosic ethanol via high-gravity technology (lignocellulosic media containing from 15 to 20% dry weight of biomass). For every type of biomass (pine chips, beech chips and wheat straw), a solvent was selected to be used during the pretreatment, guaranteeing the acquisition of a medium highly susceptible to the process of enzymatic hydrolysis.ResultsThe highest efficiency of the hydrolysis of biomass, amounting to 71.14 ± 0.97% (glucose concentration 109.26 ± 3.49 g/L) was achieved for wheat straw subjected to microwave-assisted pretreatment using 40% w/v NaCS. Fermentation of this medium produced ethanol concentration at the level of 53.84 ± 1.25 g/L. A slightly lower effectiveness of enzymatic hydrolysis (62.21 ± 0.62%) was achieved after high-pressure microwave-assisted pretreatment of beech chips using 1% w/v NaOH. The hydrolysate contained glucose in the concentration of 91.78 ± 1.91 g/L, and the acquired concentration of ethanol after fermentation amounted to 49.07 ± 2.06 g/L. In the case of pine chips, the most effective delignification was achieved using 60% v/v EtOH with the addition of 1% v/v H2SO4, but after enzymatic hydrolysis, the concentration of glucose in hydrolysate was lower than in the other raw materials and amounted to 39.15 ± 1.62 g/L (the concentration of ethanol after fermentation was ca. 19.67 ± 0.98 g/L). The presence of xylose and galactose was also determined in the obtained fermentation media. The highest initial concentration of these carbohydrates (21.39 ± 1.44 g/L) was observed in beech chips media after microwave-assisted pretreatment using NaOH. The use of wheat straw after pretreatment using EtOH with an addition of 1% v/v H2SO4 for the preparation of fermentation medium, results in the generation of the initial concentration of galactose and xylose at the level of 19.03 ± 0.38 g/L.ConclusionThe achieved results indicate a high effectiveness of the enzymatic hydrolysis of the biomass subjected to high-pressure microwave-assisted pretreatment. The final effect depends on the combined use of correctly selected solvents for the different sources of lignocellulosic biomass. On the basis of the achieved results, we can say that the presented method indicates a very high potential in the area of its use for the production of cellulosic ethanol involving high-gravity technology.

Enzymatic Cocktail Formulation for Xylan Hydrolysis into Xylose and Xylooligosaccharides.

In the context of a biorefinery, lignocellulosic materials represent an important source of raw material for the bioconversion of cellulose, hemicellulose, and lignin into value-added products, such as xylose for fermentation, oligosaccharides, and bioplastics for packaging. Among the most abundant lignocellulosic materials in Brazil, sugarcane bagasse biomass stands out, as it is rich in cellulose and hemicellulose. In this context, through an experimental design, this study developed a robust enzyme cocktail containing xylanases and accessory enzymes to complete the hydrolysis of xylan from sugarcane bagasse, obtaining a low xylose yield and concentration (9% and 1.8 g/L, respectively, observed in experiment number 16 from the complete hydrolysis of a xylan assay), a fermentable sugar that is important in the production of second-generation ethanol, and a high xylooligosaccharides (XOS) yield and concentration (93.1% and 19.6 g/L, respectively, obtained from a xylooligosaccharides production assay); in general, xylan has prebiotic activities that favor an improvement in intestinal functions, with immunological and antimicrobial actions and other benefits to human health. In addition to completely hydrolyzing the sugarcane bagasse xylan, this enzymatic cocktail has great potential to be applied in other sources of lignocellulosic biomass for the conversion of xylan into xylose and XOS due to its enzymes content, involving both main chain and pendant groups hydrolysis of hemicelluloses.

Hydrothermal pretreatment optimization of hemicellulose dissolution of sugar palm starch industrial waste

Lignocellulosic biomass is a renewable source containing three main components: cellulose, hemicellulose, and lignin. The three main components can be processed into products that have high added value. Sources of lignocellulosic biomass includes wood, grass, industrial waste, and agricultural residu. Compared to other source, industrial wastes have a higher potential to be utilized without competition for other needs and assist industry in waste treatment. The production of sugar palm starch generate biomass waste which is disposed into the environment which disturbs the surrounding community and is not utilized. To utilize lignocellulosic biomass, pretreatment is a very important step. Hydrothermal is an environmentally friendly pretreatment, without using harmful chemicals in the process. The purpose of this study was to determine the level of solubility of hemicellulose in the hydrothermal pretreatment process of sugar palm starch industrial waste. The hydrothermal method used is liquid hot water with temperature and time parameters, optimization analysis using response surface methodology (RSM). The result obtained is that the liquid hot water pretreatment method is effective in dissolving the hemicellulose from the sugar palm starch industrial waste. The relationship between variables on hemiselulosa response is modeled Y = 7.7-3.04 X1 – 5.67X2 + 0.4250 X1X2 + 1.06 X1 2 + 3.61 X2 2. The optimization results showed the optimum temperature at 195.91°C for 36.725 minutes, with a hemicellulose dissolution of 81.59% and the level of desirability is 0.852.

Pathway exploration in low-temperature oxidation of a new-generation bio-hybrid fuel 1,3-dioxane

The joint and flexible utilization of renewable electricity, ligno-cellulosic biomass, and/or CO2 point sources to produce so-called bio-hybrid fuels is a promising solution to achieve carbon neutrality while still meeting the energy demand of the transportation sector. One of the new-generation bio-hybrid fuels is 1,3-dioxane. It has a special chemical structure with two oxygen atoms in a six-membered ring. In this work, the low-temperature oxidation of 1,3-dioxane was studied theoretically and experimentally. Potential energy surfaces of the products of the O2 recombination with the three radicals formed from the H-atom abstraction of 1,3-dioxane were calculated at the DLPNO-CCSD(T)/CBS//B2PLYP-D3/cc-pVTZ level. The reaction rate coefficients were calculated with the RRKM/master equation method (T = 500–2000 K, p = 0.01–100 atm). To validate the proposed pathways, low-temperature oxidation experiments of 1,3-dioxane were performed in a jet stirred reactor (JSR) coupled with a synchrotron photon ionization time of flight molecular beam mass spectrometer (T = 590 K, p = 1 bar). Key intermediates in the investigated pathways were captured and identified by the combination of measured photon ionization efficiency curves and calculated ionization energies. Compared to cyclohexane, which has no oxygen in the six-membered ring, 1,3-dioxane has much weaker C-H bonds for the carbon between the two oxygen atoms, thus enabling faster internal H-atom migration from ROO to QOOH. Furthermore, oxidation of 1,3-dioxane tends to favor cyclic ethers + OH (chain propagation) instead of alkenes + HO2 (chain termination), explaining its high reactivity in the low-temperature regime.

Combustion and emission characteristics of diesel engine fueled with diesel/cyclohexanol blend fuels under different exhaust gas recirculation ratios and injection timings

Cyclohexanol is obtained from abundant lignocellulosic biomass sources at low cost, and it is a promising alternative fuel for diesel engines. In this study, cyclohexanol was blended with diesel at various volume ratios and the mixtures were denoted as D100 (100 % diesel + 0 % cyclohexanol), D90CH10 (90 % diesel + 10 % cyclohexanol), and D80CH20 (80 % diesel + 20 % cyclohexanol), respectively. Subsequently, the effects of exhaust gas recirculation and pilot plus main injections at various pilot injection timings on the combustion and emissions of the diesel engine fueled with various mixtures were evaluated. The results demonstrated that diesel/cyclohexanol blends had a longer ignition delay, but shorter combustion duration. D80CH20 had the highest oxygen content, peak combustion temperature (PCT), and peak heat release rate (PHRR) at medium and high loads. Cyclohexanol blending with diesel significantly decreased the particulate number (PN) and volume concentrations at the expense of higher NOx emissions. Advancing the pilot injection timing prolonged the ignition delay and combustion duration, and increased the PCT and PHRR. Therefore, it emitted higher NOx emissions, but lower PN emissions. D80CH20 with 8 % EGR can simultaneously reduce the PN and NOx emissions at medium and high loads.

Bioethanol production from coconut fiber wastes using <em>Saccharomyces cerevisiae</em>

The principal energy source of the globe at present is non-renewable fossil fuels. With the arising of global dilemmas, the human population demands new energy sources. Coconut palm wastes have been identified as an important source of lignocellulosic biomass and it is underutilized in local industries, the accumulation of fiber has become a very problematic waste in Sri Lanka. Therefore, this study was aimed to determine the efficient coconut waste material for bioethanol production and to optimize the conditions for fermentation to enhance the yield. When the coconut husk fiber was inoculated with <em>Saccharomyces cerevisiae </em>(baker’s yeast 2g/L) in the fermentation media (100ml, 8o Brix, Waste extract: distilled water = 1:3) composed of 10 g/L yeast extract, 10 g/L KH₂PO₄, 2 g/L (NH₄)₂SO₄, 2g/L peptone and 0.5 g/L MgSO₄•7H₂O and allowed for fermentation for 24h at 30⁰C and 100rpm, the ethanol yield was 0.8% V/V. When different coconut palm wastes such as mature leaves (old leaves), young leaves (green leaves), young fruit fiber (kurumba), roots and husk fiber were used as the substrate with <em>Saccharomyces cerevisiae</em>, significantly higher quantities of bioethanol were produced with young leaves (green leaves) and husk fibers. However, coconut husk fiber was selected as a bioethanol source, for further studies due to its abundance and availability in the farms, slow natural degradation, and its role in providing a breeding ground for mosquitoes. The conditions were optimized sequentially by changing one factor at a time while keeping the other variables constant. When the fermentation time was optimized with coconut husk fiber the ethanol yield was significantly increased by 4 times at the 3rd day, than non-optimized conditions. When the amount of coconut husk fiber was increased by 2.5 times (12.5g/ 100 ml), bioethanol output was significantly increased by 6.4 times. Ethanol yield was significantly increased when 3.75g/ 100ml of yeast inoculum was used, compared to the non-optimized condition (1.25g/ 100ml). When the pH of the media was optimized as 4.8, significantly higher bioethanol yield was obtained, than the control (3.8). When the solution (V): air space (V) ratio was optimized to 1:1.3, bioethanol output was significantly increased by 6.6 times compared with the non-optimized condition (1:4). Large scale multi-centre fermentation study needs to be done in order to determine commercialization.

Furfural degradation and its effect on Rhodosporidium toruloides-1588 during microbial growth and lipid accumulation

The presence of furfural in the hydrolysates obtained from lignocellulosic biomass sources represents an enormous challenge during their fermentation because furfural is a toxic compound for different microorganisms. Rhodosporidium toruloides-1588 can grow and accumulate lipids using wood hydrolysate as a substrate containing up to 1 g/L of furfural. In this study, the capacity of R. toruloides-1588 to grow and accumulate lipids using furfural without glucose in the media has been observed. R. toruloides-1588 degraded up to 3 g/L of furfural into furfuryl alcohol (1.8 g/L) and 2-furoic acid (0.9 g/L). Furthermore, R. toruloides-1588 accumulated 52% and 30% of its dry weight into lipids using YM media and YM media without glucose, respectively. Fatty acids such as palmitic, stearic and oleic were the most abundant. Finally, R. toruloides-1588 could potentially utilize furfural as a carbon source.

Biorefinery for efficient xanthan gum, ethanol, and biogas production from potato crop residues

Potato crop residues (PCR), as a naturally abundant source of lignocellulosic biomass, were used for the microbial production of xanthan gum and biofuels in the frame of two different biorefining scenarios. To enhance production yields, organosolv pretreatments with 50 and 75% (vv−1) ethanol at 120, 140, and 180 °C, in the presence or absence of (1% ww−1) H2SO4 (as a catalyst), were used before enzymatic hydrolysis. The hydrolysate of the pretreated PCR was microbially fermented to xanthan gum and ethanol through scenarios 1 and 2, respectively. Moreover, the stillages (waste residues) of both scenarios were anaerobically digested to produce biomethane. The maximum glucose yield of 74.6% was achieved after the catalytic pretreatment of PCR with 50% ethanol at 180 °C, while the yield from the untreated PCR was only 34.8%. Xanthan gum and ethanol yield from the untreated PCR were only 6.2 g xanthan gum per 100 g substrate and 27.5%, respectively. After the pretreatment at the optimum conditions, the highest xanthan gum (12.5 g per 100 g substrate) and ethanol (56.1%) yields were obtained. Moreover, the greatest biomethane yield of 196.0 mL g−1 volatile solids was obtained from the liquid fraction of organosolv pretreatment at 180 °C with 50% ethanol, in the absence of the catalyst. Overall, the highest obtained energy was 66.7 and 147.7 L gasoline equivalent per ton of PCR for scenarios 1 and 2, respectively. Scenario 1 provided an economic potential of $ 280.7, which was higher than that of the second scenario ($ 107.4).

Adsorption Phenomenon for Removal of Pb(II) via Teff Straw based Activated Carbon Prepared by Microwave-Assisted Pyrolysis: Process Modelling, Statistical Optimisation, Isotherm, Kinetics, and Thermodynamic Studies

ABSTRACT Eragrostis tef (Teff) is one of the most important staple crops in Ethiopia. The straw obtained from teff is a plentiful source of lignocellulosic biomass. In the present study, straw obtained from teff grass was exploited as a carbon precursor to synthesise the activated carbon via chemical activation followed by microwave-aided pyrolysis. The prepared activated carbon by microwave aided method from teff straw (MATSAC) was utilised as a bio-adsorbent to examine the lead II ions adsorption potential from the aqueous medium. RSM technique was employed to explore a process model which correlates the four independent variables namely Pb(II) ions initial concentration, MATSAC dose, adsorption time, and solution pH. Further, the model was statistically optimised to achieve optimum Pb(II) ions removal. They were discovered to be Pb(II) ions initial concentration: 94.35 mg/L, MATSAC dose: 0.655 g/100 mL, adsorption time: 87.6 min, and solution pH: 5.4 to achieve the maximised removal of Pb(II) (90.89%). In the investigation on the models of isotherm, it was inferred that Langmuir isotherm fitted excellently to the equilibrium data of the adsorption. The adsorption capacity of Pb(II) on MATSAC was 42.97 mg/g. In addition, the kinetic analysis confirmed that the process of adsorption was statistically significant to pseudo 2nd order. The thermodynamic study indicated that the negative value of ∆Go deep-rooted the practicability and spontaneity of MATSAC for Pb(II) ions removal. In a nutshell, MATSAC, which is derived from locally available agricultural waste, can remove toxic Pb(II) ions from contaminated water at a minimal cost.

Challenges of Biomass Utilization for Bioenergy in a Climate Change Scenario.

Simple SummaryThe most recent intergovernmental panel on climate change (IPCC 2021) has shown that the human influence on climate change has been unprecedented, predicting a global temperature increase of 1.5 °C in the earlies 2030s. The burning of fossil fuels has increased the emissions of nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2) to the atmosphere, amplifying the greenhouse effect in the last decades. In this scenario, the use of biorefineries, a renewable analog to petroleum refineries, has attracted a lot of attention since they use renewable sources as lignocellulosic feedstocks. However, climate change alters the temperature, rainfall patterns, drought, CO2 levels, and air moisture impacting biomass growth, productivity, chemical composition, and soil microbial community. Here, we discuss strategies to produce fuels and value-added products from biomass in a climate change scenario, potential feedstocks for bioenergy purposes, the chemical composition of lignocellulosic biomass, enzymes involved in biomass deconstruction, and other processes related to biomass production, processing, and conversion. Understanding these integrated factors involved in bioenergy production with plant responses to climate change shows that climate-smart agriculture is the only way to lower the negative impact of climate changes on crop adaptation and its use for bioenergy.The climate changes expected for the next decades will expose plants to increasing occurrences of combined abiotic stresses, including drought, higher temperatures, and elevated CO2 atmospheric concentrations. These abiotic stresses have significant consequences on photosynthesis and other plants’ physiological processes and can lead to tolerance mechanisms that impact metabolism dynamics and limit plant productivity. Furthermore, due to the high carbohydrate content on the cell wall, plants represent a an essential source of lignocellulosic biomass for biofuels production. Thus, it is necessary to estimate their potential as feedstock for renewable energy production in future climate conditions since the synthesis of cell wall components seems to be affected by abiotic stresses. This review provides a brief overview of plant responses and the tolerance mechanisms applied in climate change scenarios that could impact its use as lignocellulosic biomass for bioenergy purposes. Important steps of biofuel production, which might influence the effects of climate change, besides biomass pretreatments and enzymatic biochemical conversions, are also discussed. We believe that this study may improve our understanding of the plant biological adaptations to combined abiotic stress and assist in the decision-making for selecting key agronomic crops that can be efficiently adapted to climate changes and applied in bioenergy production.

Assessment of Durum Wheat (Triticum durum Desf.) Genotypes Diversity for the Integrated Production of Bioethanol and Grains

Wheat straw is an abundant source of lignocellulosic biomass that is generally not utilized for biofuel production, nor for other uses. Recent EU renewable energy directive fosters bioethanol production through lignocellulosic sugars fermentation, but the cost of this process is an issue that often depends on biomass characteristics. Lignin is a class of three-dimensional polymers providing structural integrity of plant tissues. Its complex structure, together with hemicelluloses and uronic acids content, could affect the ability of hydrolyzing biomass to fermentable sugars. To get insights into this variation, a set of 10 durum wheat genotypes was analyzed to determine variation of straw digestibility to fermentable sugars. The results showed that the lignin content was the major factor determining the recalcitrance to enzymatic process. The analysis of Spearman’s correlation indicated that the sugar released after enzymatic hydrolysis had a negative connection with the lignin content, while it was positively correlated with the culm length. The possible role of other cell wall components, such as arabinose and uronic acids, was also discussed. This work aimed at analyzing the diversity of lignocellulosic digestibility to fermentable sugars of wheat straw in a small germplasm collection. Some of the selected genotypes were characterized by high sugars digestibility and high grain yield, characteristics that could make biorefining of wheat straw profitable.

Structural and chemical characterization of hop bine fibers and their applications in the paper industry

The growth in the Humulus lupulus L. or hops industry, a perennial species, driven by demand from brewers has had annual revenue growth of 11.3% since 2015 making it one of the fastest growing agricultural commodities in the Pacific Northwest (PNW). There is currently 85,000 MT per year of hop bine in the PNW available for paper making. The land dedicated to hop agriculture increased by 68% from 2010 to 2019 in the Yakima Valley. The plant Humulus lupulus L. belongs to the same family as Cannabis sativa L., industrial hemp, which has seen practical use in both the paper industry and in the biobased development. The bulk density of the hop bine is low, 0.296 g/cm3 and only 1.5 metric tons of bine is produced per acre each year. However, as crops allocated to production of renewable resources compete for land previously dedicated to food crops, the residual biomass from hop cultivation offers an inexpensive alternative source of renewable lignocellulosic biomass without cannibalizing a food crop. H. lupulus was characterized to evaluate the acceptability for use as a paper making fiber and for hydrolytic conversion to biobased products. The high carbohydrate content, 58%, is similar to other lignocellulosic materials suitable for bioenergy feedstocks. The fiber has morphological characteristics similar to hardwood with length and width centered around 0.85 mm and 16.5 µm, respectively. The tensile strength of the hop-made papers was 61% greater than the industrial hemp made papers at the same refining level. This fiber presents a sustainable multi-use commodity with excellent application in biobased products and paper making which would otherwise be lost.

Resource recovery of lignocellulosic biomass waste into lactic acid - Trends to sustain cleaner production

Biomass waste generation concerns regulatory authorities to develop novel methods to sustain biotransformation processes. Particularly, lactic acid (LA) is a bulk commodity chemical used in diverse industries and holds a growing global market demand. Recently, lignocellulosic waste biomass is preferred for LA bio-production because of its non-edible and inexpensive nature. However, the information about new pretreatment methods for lignocellulosic feedstock, and novel strains capable to produce LA through fermentation is limited. Therefore, this review highlights the advancement of pretreatments methods of lignocellulosic biomass and biotransformation. Herein, we first briefly explored the main sources of lignocellulosic waste biomass, then we explored their latest advances in pretreatment processes particularly supercritical fluid extraction, and microwave-assisted extraction. Approaches for bioconversion were also analyzed, such as consolidated bioprocessing (CBP), simultaneous saccharification and fermentation (SSF), separate hydrolysis fermentation (SHF), among other alternatives. Also, new trends and approaches were documented, such as metagenomics to find novel strains of microorganisms and the use of recombinant strategies for the creation of new strains. Finally, we developed a holistic and sustainable perspective based on novel microbial ecology tools such as next-gen sequencing, bioinformatics, and metagenomics. All these shed light on the needs to culture powerful microbial isolates, co-cultures, and mixed consortia to improve fermentation processes with the aim of optimizing cultures and feedstock pretreatments.

Milling as a route to porous graphitic carbons from biomass.

This paper reports a simple way to produce porous graphitic carbons from a wide range of lignocellulosic biomass sources, including nut shells, softwood sawdust, seed husks and bamboo. Biomass precursors are milled and sieved to produce fine powders and are then converted to porous graphitic carbons by iron-catalysed graphitization. Graphitizing the raw (unmilled) biomass creates carbons that are diverse in their porosity and adsorption properties. This is due to the inability of the iron catalyst precursor to penetrate the structure of dense biomass material. Milling enables much more efficient impregnation of the biomass and produces carbons with homogeneous properties. Lignocellulosic biomass (particularly waste biomass) is an attractive precursor to technologically important porous graphitic carbons as it is abundant and renewable. This simple method for preparing the biomass enables a wide range of biomass sources to be used to produce carbons with homogeneous properties.This article is part of the theme issue ‘Bio-derived and bioinspired sustainable advanced materials for emerging technologies (part 2)’.

Modeling a Biorefinery: Converting Pineapple Waste to Bioproducts and Biofuel

Many students may not be aware that renewable biological materials can be converted into multiple bioproducts and biofuels using a biorefinery process, a more sustainable alternative to conventional crude oil refineries. By using waste from pineapple, a plant material that most students are familiar with, a biorefinery can be modeled to demonstrate the benefits of a circular bioeconomy. Pineapple waste consists of the peel, core, and leaves that are often discarded after the fruit is processed for consumption. These “leftovers” or “residues” are rich sources of sugars and lignocellulosic biomass, which can be converted to value-added bioproducts and biofuel. In this article, the development and implementation of a high school laboratory activity that simulates a pineapple biorefinery is described. It was field tested with an Environmental Science class, in which students converted pineapple leaves into paper, and they fermented the sugars from the core and peel into bioethanol for fuel. Students investigated how different process variables influenced the tensile strength of their paper and the quantity of bioethanol produced. This lab introduces students to the potential of a circular bioeconomy and challenges them to integrate prior chemistry and biology knowledge to generate solutions to real-world sustainability problems. It can be used in chemistry classes to demonstrate stoichiometry, chemical reaction yield, chemical bonds, and the effect of reactant concentration on the rate of product formation.

Life cycle assessment on delignification and nanolignin synthesis pathways

Lignin, a polymeric material which constitutes about 15 – 40% of the lignocellulosic biomass in plants, is not utilized to its fullest potential as it is treated as waste and applied in low-value applications. In recent years, potential lignin applications in nanoscale have been established but the journey towards the commercialization of nanolignin (NL) is still underdeveloped. As the idea of sustainability continues to seep in, the sustainability and environmental performance of NL synthesis is vital and should be focused. Hence, life cycle assessment (LCA) with the impact assessment of global warming potential (GWP), human toxicity potential (HTP) and water depletion (WD), was conducted in this study to analyze various ecological impacts associated with the NL synthesis pathways via birch chips and oil palm empty fruit bunch (EFB). From the eight synthesis pathways analyzed, the LCA results demonstrated that birch-alkali-homogenization (BAH) pathway and EFB-organosolv-homogenization (EOH) pathway has the best overall environmental performance when birch chips and EFB are used as the lignin source, respectively. For every 1 kg of NL produced, 102.76 kg CO2 eq. of GWP, 935.49 m3 air per kg of HTP and 0.28 m3 of WD are contributed by the BAH pathway. Whereas, 1052.13 kg CO2 eq. of GWP, 1158.36 m3 air per kg of HTP and 0.61 m3 of WD are contributed by the EOH pathway. It is found that a novel delignification method like organosolv is not necessary a more ecologically benign alternative as compared to a conventional alkali pretreatment process but dependant on the source of lignocellulosic biomass.

Association mapping for maize stover yield and saccharification efficiency using a multiparent advanced generation intercross (MAGIC) population

Cellulosic ethanol derived from fast growing C4 grasses could become an alternative to finite fossil fuels. With the potential to generate a major source of lignocellulosic biomass, maize has gained importance as an outstanding model plant for studying the complex cell wall network and also to optimize crop breeding strategies in bioenergy grasses. A genome-wide association study (GWAS) was conducted using a subset of 408 Recombinant Inbred Lines (RILs) from a Multi-Parent Advanced Generation Intercross (MAGIC) Population in order to identify single nucleotide polymorphisms (SNPs) associated with yield and saccharification efficiency of maize stover. We identified 13 SNPs significantly associated with increased stover yield that corresponded to 13 QTL, and 2 SNPs significantly associated with improved saccharification efficiency, that could be clustered into 2 QTL. We have pointed out the most interesting SNPs to be implemented in breeding programs based on results from analyses of averaged and yearly data. Association mapping in this MAGIC population highlight genomic regions directly linked to traits that influence the final use of maize. Markers linked to these QTL could be used in genomic or marker-assisted selection programs to improve biomass quality for ethanol production. This study opens a possible optimisation path for improving the viability of second-generation biofuels.