Biorefinery Scheme Research Articles

Efficient coproduction of butanol, ethanol, and biohydrogen from municipal solid waste through a cocultivated biorefinery

The cocultivation of Clostridium acetobutylicum and Mucor indicus was evaluated for the first time to take the advantages of both microorganisms for fully exploiting the energy potential of the organic fraction of municipal solid waste (OFMSW), generating high yields of acetone-butanol-ethanol (ABE) and hydrogen through a biorefinery scheme. Unlike M. indicus, C. acetobutylicum can ferment unhydrolyzed starch and pentose sugars. However, the low biofuel titer through ABE fermentation makes the bioprocess uneconomical. The fungal-bacterial symbiosis led to high ethanol titer along with high butanol and hydrogen yields without the need for starch hydrolysis. The effects of most influencing factors, i.e., initial pH, bacterium to fungus biomass ratio, and solid loading, on ABE and hydrogen production were investigated. The fermentation of organosolv pretreated OFMSW hydrolysate at initial pH of 5.5 and solid loading of 5% with 1:1 bacterium to fungus biomass ratio produced 80.2 g butanol, 30.2 g acetone, 108.1 g ethanol, and 96.3 L hydrogen from each kg raw OFMSW. From the bioenergy point of view, 7.2 MJ energy was generated, which was significantly higher than those obtained via the mono cultivation of C. acetobutylicum (6.2 MJ) and M. indicus (4.4 MJ), indicating the great potential of the fungal-bacterial cocultivation for bioenergy production from OFMSW. The economic potential of the cocultivated biorefinery was 0.16 $/kg OFMSW.

Producción supercrítica de biodiésel: Factibilidad de integración energética con un proceso de producción de bioetanol

Biodiesel can be obtained from raw materials with high content of free fatty acids through supercritical processes, which allows obtaining high-quality fuel; nevertheless, such processes imply operating under high pressure and temperature. On the other hand, low-cost lignocellulosic biomass can be converted to bioethanol. Both processes can be integrated through energy flows, expecting reductions on the total energy requirements and environmental impact. Therefore, in this work the integration through energy flows between biodiesel and bioethanol processes is performed, along with its impact in terms of total annual cost and environmental impact. The processes are first integrated as separated entities, then the effect of integrating both processes in a biorefinery scheme is analyzed. According to the results, the heat integration of both processes allows reducing around 15% of the total annual cost associated to heat exchangers. Moreover, the integration even allows reductions in the capital costs for the supercritical process.

Agricultural waste biorefinery development towards circular bioeconomy

The concept of biorefinery depends on the recuperation of higher-value chemicals with potential for a wide dissemination and an untapped marketability. To construct a clearer picture of rural waste treatment system, this work was conducted to critically review the foremost regularly utilized agricultural waste management technologies from their state of the art, challenges for setting up the biorefinery and system of circular economy with self-efficient business model. The drivers that can make the biorefinery concept appropriate to waste management and the conceivable outcomes for its improvement to full scale were examined. Technological, strategic and market imperatives influence the effective usage of these frameworks. This review discusses the state-of-the-art biorefinery opportunities beyond conventional strategies as an economically viable solution to overcome numerous current challenges such as waste minimization and the biosynthesis of different high-value bioproducts biorefinery strategies, integrated approach as well as economic and environmental impact were discussed.

Switchgrass as an alternative biomass for ethanol production in a biorefinery: Perspectives on technology, economics and environmental sustainability

The production of biofuels from lignocellulosic biomass is not economically viable unless it is co-produced with other marketable high value bio-based compounds using a biorefinery strategy. Advanced cellulosic biofuels derived from agricultural and forestry residues, non-food/feed energy crops or organic waste, could overcome concerns associated with conventional biofuels (impact on food prices, use of land for agricultural and forest products) and achieve large greenhouse gases emissions savings. The main obstacles to the use of advanced biofuels are availability and price of feedstocks, efficiency in conversion, reliability of the technology involved, stability of national polices, level of subsidy and mixing requirements. Switchgrass is a dedicated lignocellulosic energy crop that has great potential for bioethanol production due to its ease of adaptation to the soil in different geographical regions (use of marginal soils), its high yields, poor soil erosion, low incidence of pests and diseases, and low water and nutrient requirements. This review discusses several switchgrass-to-ethanol conversion pathways, considering different aspects of the feedstock, research on the cultivar, yield, and characteristics that have driven research to develop the perennial crop for biofuel. A comprehensive gathering of literature on alternative pretreatment methods, fermentation processes and microorganisms, co-products synthesized when fractionating multiple sugars, and biorefinery economics are presented. Meta-data about pretreatment and fermentation experimental work and how these studies have informed techno-economic analysis of bio-ethanol conversion are reported. Environmental life cycle assessment studies and to a lesser extent, socio-economic and social aspects of biofuels and dedicated energy crops like switchgrass are also reviewed.

Optimized production of xylooligosaccharides from poplar: A biorefinery strategy with sequential acetic acid/sodium acetate hydrolysis followed by xylanase hydrolysis

The preparation of xylooligosaccharides (XOS) from lignocelluloses by organic acid hydrolysis has the advantages of high efficiency and simplicity, but reducing the production of by-products, especially xylose, is a prerequisite for commercial preparation of XOS using organic acid. In this work, to reduce the production of by-products, the acetic acid/sodium acetate conjugate system (AC/SA) was used to prepare XOS from poplar. Under the optimal conditions (0.15 M AC/SA, molar ratio of 3.0, 175 °C, 60 min), the maximum XOS yield was 33.6% with a low xylose/XOS ratio of 0.19. Xylanase hydrolysis effectively converted XOS with DP above 6 in the AC/SA hydrolysate to X2-X6 with little xylose produced. The XOS yield increased to 42.1%, with a xylose/XOS ratio was only 0.17. This work shows that AC/SA in combination with xylanase hydrolysis of poplar successfully achieved high XOS yield with low by-products yields without the extraction of xylan from the substrate.

Sustainable processes for treatment and management of seafood solid waste

Seafood processing is an important economical activity worldwide and is an integral part of the food chain system. However, their processing results in solid waste generation whose disposal and management is a serious concern. Proteins, amino acids, lipids with high amounts of polyunsaturated fatty acids (PUFA), carotenoids, and minerals are abundant in the discards, effluents, and by-catch of seafood processing waste. As a result, it causes nutritional loss and poses major environmental risks. To solve the issues, it is critical that the waste be exposed to secondary processing and valorization for recovery of value added products. Although chemical waste treatment technologies are available, the majority of these procedures have inherent flaws. Biological solutions, on the other hand, are safe, efficacious, and ecologically friendly while maintaining the intrinsic bioactivities after waste conversion. Microbial fermentation or the actions of exogenously introduced enzymes on waste components are used in most bioconversion processes. Algal biotechnology has recently developed unique technologies for biotransformation of nutrients, which may be employed as a feedstock for the recovery of important chemicals as well as biofuel. Bioconversion methods combined with a bio-refinery strategy offer the potential to enable environmentally-friendly and cost-effective seafood waste management. The refinement of these wastes through sustainable bioprocessing interventions can give rise to various circular bioeconomies within the seafood processing sector. Moreover, a techno-economic perspective on the developed solid waste processing lines and its subsequent environmental impact could facilitate commercialization. This review aims to provide a comprehensive view and critical analysis of the recent updates in seafood waste processing in terms of bioconversion processes and byproduct development. Various case studies on circular bioeconomy formulated on seafood processing waste along with techno-economic feasibility for the possible development of sustainable seafood biorefineries have also been discussed.

Life cycle assessment of the Argentine lemon and its derivatives in a circular economy context

Over the last few years, a paradigm shift has emerged towards a circular economy that seeks to return to the process as many material/energy flows as possible to increase the sustainability of products, reducing waste and pollution. The citrus industry is not an exception hence one way to apply this approach is through the re-use of certain outflows to produce bioproducts and bioenergy. The objectives of this work are, first, to present the environmental profile of lemons and derivatives in Argentina through the Life Cycle Assessment methodology, and second, to unveil environmental implications of shifting from traditional industries to biorefineries which apply circular economy principles. To do that, the current production scheme for manufacturing essential oil, concentrated juices and dehydrated peel is studied (baseline), to then consider new products, i.e., ethanol, limonene and biogas, through several scenarios with different degrees of biogas recirculation. We find that for lemon production, agrochemicals represent more than 60% in eleven of the twelve impact categories. For processed products, agriculture contributes with more than 50% in all the categories, followed by natural gas and electricity consumption. It also results that adding value to wastes and implementing circular economy strategies do not ensure a better environmental performance of the system. When comparing the current situation with biorefinery schemes, the most promising scenario is the one in which all the biogas is used to produce electricity, causing the least impact in eight of the twelve categories analyzed.

Strategies for converting non-edible biomass into value-added chemicals: Economical and reliable biorefining processes

About 35% of global greenhouse gas (GHG) emissions come from the energy sector, which accelerates global warming and sea-level rise. As a renewable resource, biomass not only can replace conventional fossil energy with renewable energy, but it is also a key component of the circular bioeconomy (CBE). To achieve efficient use of bioresources, the concept of biorefinery with CBE strategy is increasingly being considered in several countries. In particular, it aims to reduce crude oil consumption and build an economy that is favorable for the climate and nature by replacing carbon-intensive products such as plastics, synthetic rubber, and synthetic fibers with renewable bio-based resources. The purpose of this article is to investigate biomass conversion technologies for building a CBE and to consider successful biorefinery strategies. In particular, five implications of using biomass are suggested as ways to secure the economic feasibility of biorefinery. We propose a biorefinery that produces value-added chemicals from non-edible biomass through saccharification and fermentation as a strategy to achieve the 2050 goal of net-zero carbon.

A sustainable and profitable biorefinery strategy for efficiently converting lignocellulose to furfural, glucose and phenolic compounds

The sustainability and profitability of biorefineries are based on efficient utilization of all components of lignocellulosic biomass.

Combining Phytoremediation and Biorefinery Strategies Assisted by an Ecofriendly Zwitterionic Ionic Liquid: A New Challenge for a Cleaner Bioeconomy

Combining Phytoremediation and Biorefinery Strategies Assisted by an Ecofriendly Zwitterionic Ionic Liquid: A New Challenge for a Cleaner Bioeconomy

Integrated Cascade Biorefinery Processes to Transform Woody Biomass Into Phenolic Monomers and Carbon Quantum Dots.

A novel cascade biorefinery strategy toward phenolic monomers and carbon quantum dots (CQDs) is proposed here via coupling catalytic hydrogenolysis and hydrothermal treatment. Birch wood was first treated with catalytic hydrogenolysis to afford a high yield of monomeric phenols (44.6 wt%), in which 4-propanol guaiacol (10.2 wt%) and 4-propanol syringol (29.7 wt%) were identified as the two major phenolic products with 89% selectivity. An available carbohydrate pulp retaining 82.4% cellulose and 71.6% hemicellulose was also obtained simultaneously, which was further used for the synthesis of CQDs by a one-step hydrothermal process. The as-prepared CQDs exhibited excellent selectivity and detection limits for several heavy metal cations, especially for Fe3+ ions in an aqueous solution. Those cost-efficient CQDs showed great potential in fluorescent sensor in situ environmental analyses. These findings provide a promising path toward developing high-performance sensors on environmental monitoring and a new route for the high value-added utilization of lignocellulosic biomass.

Electrogenerated alkaline hydrogen peroxide pretreatment of waste wheat straw to enhance enzymatic hydrolysis

Discovering low-cost and green pretreatments for efficient deconstruction of lignocellulosic biomass recalcitrance is receiving growing interests. Herein, a novel electrogenerated alkaline hydrogen peroxide (EAHP) pretreatment was first proposed to produce H2O2 and pretreat biomass concurrently in one pot. Results showed that the home-made electrode possess superior selectivity and stability. Under the optimal condition (30 mA·cm−2, 70 °C, 4 h), the novel pretreatment removed 76.3% of lignin while preserving cellulose, and the specific surface area and porosity of pretreated WS were greatly increased. The chemical and structural changes stimulated the enzymatic hydrolysis of cellulose and xylan reaching a maximum value of 83.7% and 90.8% respectively, which were significantly enhanced 4.1- and 5.3-fold compared to the original biomass. Overall, this work proposed a feasible biorefinery strategy for effective fractionation and utilization of lignocellulosic biomass.

Impact of the lignin type and source on the characteristics of physical lignin hydrogels

Multiple natural polymers have been investigated for the synthesis of hydrogels to the present date, but lignin has demonstrated to be a promising one for this purpose for the multiple advantages it offers. Lignin can be isolated from lignocellulosic material such as nut shells, which are usually undervalued wastes, and would be a great step forward on circular economy. Thus, in the present work, lignin was extracted from almond and walnut shells following a single-step (delignification) and double-step (autohydrolysis and delignification) biorefinery scheme. After the chemical composition and structures of these lignins were determined, hydrogels were synthesized combining them with poly (vinyl alcohol) by the means of freeze-thawing cycles so as to study the influence of the different lignins on their final properties. Additionally, the last thawing cycle of the synthesis process was lengthened in order to confirm previous assumptions about its effect on the characteristics of the synthesized materials. The obtained results showed significant variation between the 8 lignin samples, especially in their purity, molecular weights and total phenolic contents. The variation on the lignins leaded to several hydrogel morphologies, which directly affected their properties, primarily their swelling capacity, glass transition temperatures and compression strengths. It was also demonstrated the great effect that the duration of the last thawing had on the morphology and, hence, on the characteristics of the obtained materials. The synthesized samples were successfully employed as dye adsorbents and the evaluation of their antifungal activity showed positive results in some of the samples, which could be applied for food packaging.

PHBMT1, a BAHD-family monolignol acyltransferase, mediates lignin acylation in poplar

Poplar (Populus) lignin is naturally acylated with p-hydroxybenzoate ester moieties. However, the enzyme(s) involved in the biosynthesis of the monolignol–p-hydroxybenzoates have remained largely unknown. Here, we performed an in vitro screen of the Populus trichocarpa BAHD acyltransferase superfamily (116 genes) using a wheatgerm cell-free translation system and found five enzymes capable of producing monolignol–p-hydroxybenzoates. We then compared the transcript abundance of the five corresponding genes with p-hydroxybenzoate concentrations using naturally occurring unrelated genotypes of P. trichocarpa and revealed a positive correlation between the expression of p-hydroxybenzoyl-CoA monolig-nol transferase (pHBMT1, Potri.001G448000) and p-hydroxybenzoate levels. To test whether pHBMT1 is responsible for the biosynthesis of monolignol–p-hydroxybenzoates, we overexpressed pHBMT1 in hybrid poplar (Populus alba × P. grandidentata) (35S::pHBMT1 and C4H::pHBMT1). Using three complementary analytical methods, we showed that there was an increase in soluble monolignol–p-hydroxybenzoates and cell-wall-bound monolignol–p-hydroxybenzoates in the poplar transgenics. As these pendent groups are ester-linked, saponification releases p-hydroxybenzoate, a precursor to parabens that are used in pharmaceuticals and cosmetics. This identified gene could therefore be used to engineer lignocellulosic biomass with increased value for emerging biorefinery strategies.

Multiobjective optimization of the supply chain for the production of biomass-based fuels and high-value added products in Mexico

Due to the growing concern about the increase in the concentration of greenhouse gases in the atmosphere, as well as the depletion of oil reserves, biofuels have become increasingly important. Human activity, mainly in the industrial and transportation sectors, is one of the main causes of the above scenario. Bioethanol and biobutanol have emerged as possible solutions to this problem, however, their production is not economically competitive. Therefore, in addition to biofuel production, the generation of high value-added products in a biorefinery scheme is mandatory to improve the economic potential of the biomass-based industry. Mexico is a country with a high agricultural production, which implies a high production of agricultural waste. Therefore, this work proposes the development of a mathematical model for the supply chain of biofuels and bioproducts production. This model is a multi-objective optimization problem through generalized disjunctive programming. The GDP model is relaxed and solved in its equivalent mixed integer linear programming form using GAMS software. The model analyzes the production of bioethanol and/or biobutanol to satisfy at least 10% of the gasoline demand in the country, as well as the production of high value-added products; considering economic, environmental, economic and social objectives. Pareto-optimal solutions were obtained using the ε constraint method and selecting the best option by the Pythagorean theorem of the Eucladian distance. According to the results, biobutanol production is the process that maintains the greatest compromise between the four objective functions, achieving a balance. On the other hand, bioethanol production is only feasible if the water footprint is disregarded, as high values are obtained, which leads to a problem of water distribution to carry out the process.

Analysis of the Phytochemical Composition of Pomegranate Fruit Juices, Peels and Kernels: A Comparative Study on Four Cultivars Grown in Southern Italy.

The increasing popularity of pomegranate (Punica granatum L.), driven by the awareness of its nutraceutical properties and excellent environmental adaptability, is promoting a global expansion of its production area. This investigation reports the variability in the weight, moisture, pH, total soluble solids, carbohydrates, organic acids, phenolic compounds, fatty acids, antioxidant activities, and element composition of different fruit parts (juices, peels, and kernels) from four (Ako, Emek, Kamel, and Wonderful One) of the most widely cultivated Israeli pomegranate varieties in Salento (South Italy). To the best of our knowledge, this is the first systematic characterization of different fruit parts from pomegranate cultivars grown simultaneously in the same orchard and subjected to identical agronomic and environmental conditions. Significant genotype-dependent variability was observed for many of the investigated parameters, though without any correlation among fruit parts. The levels of phenols, flavonoids, anthocyanins, and ascorbic and dehydroascorbic acids of all samples were higher than the literature-reported data, as was the antioxidant activity. This is likely due to positive interactions among genotypes, the environment, and good agricultural practices. This study also confirms that pomegranate kernels and peels are, respectively, rich sources of punicic acid and phenols together, with several other bioactive molecules. However, the variability in their levels emphasizes the need for further research to better exploit their agro-industrial potential and thereby increase juice-production chain sustainability. This study will help to assist breeders and growers to respond to consumer and industrial preferences and encourage the development of biorefinery strategies for the utilization of pomegranate by-products as nutraceuticals or value-added ingredients for custom-tailored supplemented foods.

Effective bioremediation of tobacco wastewater by microalgae at acidic pH for synergistic biomass and lipid accumulation

Tobacco wastewater is too difficult to decontaminate which poses a significant environmental problem due to the harmful and toxic components. Chlorella pyrenoidosa is a typical microalgal species with potential in removal of organic/inorganic pollutants and proves to be an ideal algal-based system for wastewater treatment. However, the strategy of tobacco related wastewater treatment using microalgae is in urgent need of development. In this study, C. pyrenoidosa was used to evaluate the removal efficiency of artificial tobacco wastewater. Under various solid-to-liquid (g/L) ratios, 1:1 ratio and acidic pH 5.0 were optimal for C. pyrenoidosa to grow with high performance of removal capacity to toxic pollutants (such as COD, NH3-N, nicotine, nitrosamines and heavy metals) with the alleviation of oxidative damage. Algal biomass could reach up to 540.24 mg/L. Furthermore, carbon flux of C. pyrenoidosa was reallocated from carbohydrate and protein biosynthesis to lipogenesis with a high lipid content of 268.60 mg/L at pH 5.0. Overall, this study demonstrates an efficient and sustainable strategy for tobacco wastewater treatment at acidic pH with the production of valuable microalgal products, which provides a promising biorefinery strategy for microalgal-based wastewater bioremediation.

Species-specific responses in pigments and fatty acids of five freshwater chlorophytes exposed to varying cultivation conditions

Microalgae have attracted increasing interests within several industrial sectors. Their diversity, underpinned by complex polyphyletic origins, represents an under-exploited source of high-value metabolites. Five freshwater chlorophytes (Ankistrodesmus sp., Pediastrum sp., Kirchneriella sp., Chloromonas sp. and Scenedesmus sp.) were grown under varying cultivation conditions including high nitrate supply, phytohormone supplementation, exposure to the herbicide molinate and exposure to blue LED light.When exposed to molinate (2.5 μg. mL−1), Kirchneriella sp. returned the highest lutein cellular content (4.9 mg. g−1). Zeaxanthin production (4.1 mg. g-1) was also highest for Scenedesmus sp. when molinate was introduced to the cultivation medium. Only Chloromonas sp. contained eicosapentaenoic acid (EPA), which returned the highest cellular content (2.6 mg. g−1) when the culture was supplemented with the phytohormone indole-3-acetic acid (2.5 μg. mL−1). Scenedesmus sp. showed an increase in the proportions of alpha-linolenic acid (∼55 %) when grown in medium enriched in nitrate. Overall, molinate supplementation enhanced the accumulation of lutein, β-β-carotene and chlorophyll a in Kirchneriella sp.These chlorophytes showed a species rather than treatment-specific response with regards to pigment cellular contents and fatty acid profiles, re-enforcing the notion that the optimisation of intracellular contents of valuable metabolites as part of a tailored biorefinery strategy needs to be considered at the species level.

Effects of P-Coumarate 3-Hydroxylase Downregulation on the Compositional and Structural Characteristics of Lignin and Hemicelluloses in Poplar Wood (Populus alba × Populus glandulosa).

Elucidating the chemical and structural characteristics of hemicelluloses and lignin in the p-coumarate 3-hydroxylase (C3H) down-regulated poplar wood will be beneficial to the upstream gene validation and downstream biomass conversion of this kind of transgenic poplar. Herein, the representative hemicelluloses and lignin with unaltered structures were prepared from control (CK) and C3H down-regulated 84K poplars. Modern analytical techniques, such as 13C NMR, 2D-HSQC NMR, and gel chromatography (GPC), were performed to better delineate the structural changes of hemicelluloses and lignin caused by transgenesis. Results showed that both the hemicelluloses (H-CK and H-C3H) extracted from control and C3H down-regulated poplar wood have a chain backbone of (1→4)-β-D-Xylan with 4-O-Me-α-D-GlcpA as side chain, and the branch degree of the H-C3H is higher than that of H-CK. With regarding to the lignin macromolecules, NMR results demonstrated that the syringyl/guaiacyl (S/G) ratio and dominant substructure β-O-4 linkages in C3H down-regulated poplar were lower than those of control poplar wood. By contrast, native lignin from C3H down-regulated poplar wood exhibited higher contents of p-hydroxybenzoate (PB) and p-hydroxyphenyl (H) units. In short, C3H down-regulation resulted in the chemical and structural changes of the hemicelluloses and lignin in these poplar wood. The identified structures will facilitate the downstream utilization and applications of lignocellulosic materials in the biorefinery strategy. Furthermore, this study could provide some illuminating results for genetic breeding on the improvement of wood properties and efficient utilization of poplar wood.

Cutaneotrichosporon oleaginosus: A Versatile Whole-Cell Biocatalyst for the Production of Single-Cell Oil from Agro-Industrial Wastes

Cutaneotrichosporon oleaginosus is an oleaginous yeast with several favourable qualities: It is fast growing, accumulates high amounts of lipids and has a very broad substrate spectrum. Its resistance to hydrolysis by-products makes it a promising biocatalyst for custom tailored microbial oils. C. oleaginosus can accumulate up to 60 wt.% of its biomass as lipids. This species is able to grow by using several compounds as a substrate, such as acetic acid, biodiesel-derived glycerol, N-acetylglucosamine, lignocellulosic hydrolysates, wastepaper and other agro-industrial wastes. This review is focused on state-of-the-art innovative and sustainable biorefinery schemes involving this promising yeast and second- and third-generation biomasses. Moreover, this review offers a comprehensive and updated summary of process strategies, biomass pretreatments and fermentation conditions for enhancing lipid production by C. oleaginosus as a whole-cell biocatalyst. Finally, an overview of the main industrial applications of single-cell oil is reported together with future perspectives.