Production Of Bio-based Chemicals Research Articles

Hydrogen-free deoxygenation of oleic acid on acidic and basic ZSM-5 and Y-zeolites: products for biofuel and reaction pathways

A large volume of highly acidic vegetable oils generated as waste could be utilized to produce low-cost biofuels without competing with food production. This study investigated the conversion of oleic acid (OA), used as a model fatty compound, in a micropyrolysis apparatus under conditions similar to those employed in fluidized catalytic cracking (FCC) of petroleum feedstocks. The influence of small-micropore size zeolites (ZSM-5) and large-micropore size zeolites (Y), in both their acidic H- and basic Na-forms, on the product distribution was evaluated. Oleic acid was pre-adsorbed onto the zeolites at a mass ratio Catalyst:OA = 10:1. Thermal cracking of pure oleic acid was limited, predominantly producing linear 1-alkenes and carboxylic acids. Conversion in the presence of catalysts was enhanced, resulting in the formation of a greater variety of hydrocarbons. Branched and cyclic alkanes, as well as polyaromatics hydrocarbons, were produced in greater quantities on Y zeolites compared to ZSM-5, due to the larger micropore diameter of the Y zeolite. Among the catalysts, Na-Y produced the highest number of hydrocarbons, predominantly within the gasoline range. These results are promising for the co-processing of fatty residues in the FCC, promoting the production of second-generation drop-in biofuels and bio-based chemicals, and contributing to industrial decarbonization.

Sustainable Production of Lactic Acid Using a Perennial Ryegrass as Feedstock—A Comparative Study of Fermentation at the Bench- and Reactor-Scale, and Ensiling

Perennial ryegrass (Lolium perenne) is an underutilized lignocellulosic biomass that has several benefits such as high availability, renewability, and biomass yield. The grass press-juice obtained from the mechanical pretreatment can be used for the bio-based production of chemicals. Lactic acid is a platform chemical that has attracted consideration due to its broad area of applications. For this reason, the more sustainable production of lactic acid is expected to increase. In this work, lactic acid was produced using complex medium at the bench- and reactor scale, and the results were compared to those obtained using an optimized press-juice medium. Bench-scale fermentations were carried out in a pH-control system and lactic acid production reached approximately 21.84 ± 0.95 g/L in complex medium, and 26.61 ± 1.2 g/L in press-juice medium. In the bioreactor, the production yield was 0.91 ± 0.07 g/g, corresponding to a 1.4-fold increase with respect to the complex medium with fructose. As a comparison to the traditional ensiling process, the ensiling of whole grass fractions of different varieties harvested in summer and autumn was performed. Ensiling showed variations in lactic acid yields, with a yield up to 15.2% dry mass for the late-harvested samples, surpassing typical silage yields of 6–10% dry mass.

Synthesis of medium-chain fatty acids from corn stover by sequential fermentation based on substrate configuration and initial pH optimization

This work describes a novel sequential fermentation method for the production of medium-chain fatty acids (MCFAs) from corn stover, without adding exogenous electron donors/acceptors. The effects of the carbon substrate concentration, ethanol-to-acetate ratio (ED/EA), and initial pH on carbon chain elongation (CCE) by Clostridium kluyveri to produce MCFAs are investigated using ethanol and acetate as the electron donor and acceptor, respectively. A carbon substrate concentration of 300 mM C is sufficient for CCE. An initial weakly alkaline environment significantly enhances the production of caproate through buffering effects and by reducing inhibition of product formation. The maximum caproate production reached 4.41 g/L (initial pH 8.5; 300 mm C; ED/EA = 1:1). The ability of corn stover to generate a suitable ED/EA via two-step fermentation to synthesize MCFAs is also explored. Ultimately, 5.53 g/L butyrate and caproate can be obtained from corn stover, where caproate accounts for 2.79 g/L. This study offers innovative ideas for the sustainable production of bio-based chemicals.

Maximizing biomass utilization: An integrated strategy for coproducing multiple chemicals

Lignocellulosic biomass is one of the viable solutions to alleviate the global warming. However, the limited utilization of biomass majorly focused on cellulose and hemicellulose restricts the economic and environmental feasibilities. To cope with this issue, we proposed an integrated process of co-producing 1,6-hexanediol (1,6-HDO) with tetrahydrofuran and adipic acid from biomass, referred to as Strategy A. To compare the impacts of lignin upgrading and feedstock, Strategy B, which co-produces tetrahydrofuran alone, and Strategy C, which is the traditional route to produce 1,6-HDO from fossil fuels, were used. Heat networks are also designed to reduce operating costs and indirect carbon emissions due to energy consumption, saving 87% and 83% of the heat and cooling requirements, respectively, in Strategy A. The market competitiveness of Strategy A was evaluated by determining the minimum selling price through techno-economic analysis, and sustainability was thoroughly investigated by quantifying the environmental impacts through both midpoint and endpoint life-cycle assessments (LCAs). Strategy A was found to be the most favorable both economically (US$3,402/ton) and environmentally (−26.9 kg CO2 eq.). This indicates that lignin valorization is not only economically but also environmentally preferred. Finally, changes in economic and environmental feasibilities depending on economic, process, and environmental parameters were investigated using sensitivity and uncertainty analyses. The results of these analyses provide valuable insight into bio-based chemical production.

Brewery spent grain valorization through fermentation: Targeting biohydrogen, carboxylic acids and methane production

This study investigated three different fermentation approaches to explore the potential for producing biohydrogen, carboxylic acids, and methane from hydrolysates of thermally dilute acid pretreated brewer's spent grains (BSG). Initially, the research focused on maximizing the volumetric hydrogen production rate (HPR) in the continuous dark fermentation (DF) of BSG hydrolysates by varying the hydraulic retention time (HRT). The highest HPR reported to date of 5.9 NL/L-d was achieved at 6 h HRT, with a Clostridium-dominated microbial community. The effect of the operational pH (4, 5, 6, and 7) on the continuous acidogenic fermentation was then investigated. A peak carboxylic acid concentration of 17.3 g CODequiv./L was recorded at pH 6, with an associated volumetric productivity of 900.5 ± 13.1 mg CODequiv./L-h and a degree of acidification of 68.3 %. Lactic acid bacteria such as Limosilactobacillus and Lactobacillus were dominant at pH 4–5, while Weissella, Enterococcus, and Lachnoclostridium appeared at pH 6 and 7. Finally, this study evaluated the biochemical methane potential of the DF broth and the unfermented hydrolysates and found high methane yields of 659 and 517 NmL CH4/g-VSadded, respectively, both within one week. Overall, the results showed that pretreated BSG can be a low-cost feedstock for the production of bioenergy and valuable bio-based chemicals in a circular economy.

Highly-efficient synthesis of 5-Hydroxymethylfurfural from fructose in micropacked bed Reactors: Multiphase Transport, reaction Optimization, and heterogeneous kinetic study

The efficient synthesis of the platform chemical 5-hydroxymethylfurfural (HMF) is of great significance for the production of downstream value-added bio-based chemicals. Herein, the highly-efficient and continuous synthesis of HMF is demonstrated in micropacked bed reactors (μPBRs) with HND-580. 95.3 % fructose conversion, 90.2 % HMF yield, and 99.3 % HMF extraction efficiency can be achieved within 26.3 s in μPBRs. The space–time yield (STY) of μPBRs is more than two times of magnitude greater than conventional fixed bed reactors (FBRs) and stirred tank reactors (STRs). The organic phase liquid holdup of liquid–liquid system is obtained at the range of 0.82–0.90, which is measured for the first time in μPBRs. The liquid–liquid mass transfer coefficient of μPBRs is 1.68 × 10-2 to 1.68 × 10-1 s−1, which is 1–3 orders of magnitude larger than STRs and packed columns. In addition, a heterogeneous kinetic model for the synthesis of HMF in water-MIBK biphasic system is established in μPBRs. The fructose conversion and HMF yield were predicted and the error was within ± 20 %.

Microwave-enhanced catalytic conversion of fatty acid ester to olefins by Na-ZSM-5

The bio-based production of essential chemicals is important for the sustainability of the chemical industry. Here, we demonstrate efficient olefin production from methyl oleate using Na substituted ZSM-5 (Na-ZSM-5) and microwave irradiation. Na-ZSM-5 exhibits superior microwave heating properties compared to H-ZSM-5 and other zeolites. It was more effective in converting methyl oleate to olefins such as ethylene and propylene than H-ZSM-5 or Y zeolites. Microwave irradiation promoted the conversion efficiency of methyl oleate by Na-ZSM-5, achieving an olefin yield over four times higher than that obtained with conventional heating (CH) using an electric furnace. Meanwhile, the aromatization to benzene, toluene and xylene (BTX) was suppressed using Na-ZSM-5, which was attributed to the removal of strong acid sites. In addition, in situ microwave XRD revealed that microwaves promoted temperature-dependent structural changes in Na-ZSM-5 at lower temperatures than CH, suggesting that microwaves form localized high temperatures in the zeolite. These localized high temperatures effectively enhance olefin production via microwave irradiation.

Hydrolysis of Babool wood biomass using carbocation scavengers assisted ionic liquid pretreatment for the production of sugars and furfurals

The present study highlights the performance of carbocation scavengers for the pretreatment of hardwood biomass followed by the production of bio-based products. The behaviour of different carbocation scavengers namely; 2-Napthol, 4 Hydroxybenzoic acid, Vanillic acid, Catechol, Hydroquinone, Resorcinol and Phenol and their mitigating effect on the rate of hydrolysis was explored under different operating conditions. All the carbocation scavengers show significant changes in the crystallinity index leading to distinct morphological and physiochemical changes in the biomass structure. Results revealed that the addition of carbocation scavengers not only reduces the inhibitory effect of structured lignin but also enhances the accessibility of cellulose and hemicellulose and facilitates the production of sugars and 5-Hydroxymethyl Furfural. Maximum 5-HMF yield was observed using 2-Napthol at an optimised concentration of 2 wt% (1.5 mL) at 190 °C in 60 min. Further, to evaluate the effect of acetyl groups, biomass deacetylation was also performed. The highest deacetylation effect was observed at 170 °C and showed ∼73% and ∼94% reduction in the holocellulosic content in 60 min. The proposed study develops a sustainable and viable route to suppress the inhibitory effect of lignin with the utilization of carbocation scavengers and enhances biomass digestibility that favours the production of bio-based chemicals.

Biorefinery of red seaweed Palmaria palmata for production of bio-based chemicals and biofuels

The seaweed Palmaria palmata was used as feedstock for production of chemical/fuel precursors (acetone, butanol, ethanol) and biogas. Palmaria palmata consists of xylan as major cell wall polysaccharide, as well as galactan and glucan. First, the biomass was subjected to acid hydrolysis at laboratory scale to solubilise fermentable sugars using acetic or hydrochloric acid as catalysts. Differences were observed in composition and amenability to hydrolysis of seaweeds from different harvests. Highest saccharification yields were obtained using HCl (pH 1.7, 120 °C, up to 80 % of xylose). Hydrolysates were fermented to acetone-butanol-ethanol by Clostridium beijerinckii reaching yields of 0.28 g products/g consumed sugars. The process by-products (solids after acetic acid hydrolysis and spent fermentation broth) were used as feedstocks for anaerobic digestion showing biogas yields between 310 and 650 L/kg dry organic material when mixed in different ratios with sugar beet pulp. Subsequently, the hydrolysis and fermentation processes were upscaled up to a 100-L pilot volume where nanofiltration was implemented to increase sugar concentration and remove salts. While high monomeric sugar yields were replicated during upscaling, fermentation inhibition was observed in the upscaled process. This paper shows Palmaria palmata to be a suitable feedstock for the co-production of bio-butanol and biogas and highlights process development needs to desalt and detoxify seaweed hydrolysates prior to fermentation.

Modulating metabolism through synthetic biology: Opportunities for two-stage fermentation.

Bio-based production of fuels, chemicals and materials is needed to replace current fossil fuel based production. However, bio-based production processes are very costly, so the process needs to be as efficient as possible. Developments in synthetic biology tools has made it possible to dynamically modulate cellular metabolism during a fermentation. This can be used towards two-stage fermentations, where the process is separated into a growth and a production phase, leading to more efficient feedstock utilization and thus potentially lower costs. This article reviews the current status and some recent results in application of synthetic biology tools towards two-stage fermentations, and compares this approach to pre-existing ones, such as nutrient limitation and addition of toxins/inhibitors.

Comparative genomics of Clostridium tyrobutyricum reveals signatures of environment-specific adaptation and metabolic potentials

Clostridium tyrobutyricum is a promising microbial host for the anaerobic production of bio-based chemicals, especially butyric acid. However, the limited genetic traits of C. tyrobutyricum resulted in its constrained applicability in the food industry due to the absence of publicly available data. We performed a comparative genomic analysis of 13 C. tyrobutyricum strains isolated from different habitats to investigate the adaptation mechanisms and metabolic potentials of the C. tyrobutyricum strains isolated from fermentation environments (FE). The results showed that the genetic diversity of FE- associated C. tyrobutyricum strains was higher than that of strains isolated from non-fermentation environments (NFE). Based on evaluating safety-related genes, FE-associated strains were likely non-pathogenic to humans or animals. Many environmental adaptation-related genes involved in energy production and conversion, phosphotransferase system (PTS), etc., were significantly enriched in FE-associated strains, which was conducive to their survival in the corresponding habitats. The analysis of carbohydrate-active enzymes revealed that the CAZyme categories of glycoside hydrolases (GHs) and carbohydrate esterases (CEs) were found to be significantly enriched in FE-associated strains, which was beneficial for carbohydrate utilization (including starch, cellulose, etc.). Fermentation experiments revealed that strains isolated from the Chinese liquor fermentation environment were capable of decomposing carbohydrates and producing organic acids. Collectively, this study provided insights into the genomic features of C. tyrobutyricum and the theoretical basis for further use, research, and development of these strains.

DetSpace: a web server for engineering detectable pathways for bio-based chemical production.

Tackling climate change challenges requires replacing current chemical industrial processes through the rational and sustainable use of biodiversity resources. To that end, production routes to key bio-based chemicals for the bioeconomy have been identified. However, their production still remains inefficient in terms of titers, rates, and yields; because of the hurdles found when scaling up. In order to make production more efficient, strategies like automated screening and dynamic pathway regulation through biosensors have been applied as part of strain optimization. However, to date, no systematic way exists to design a genetic circuit that is responsive to concentrations of a given target compound. Here, the DetSpace web server provides a set of integrated tools that allows a user to select and design a biological circuit that performs the sensing of a molecule of interest by its enzymatic conversion to a detectable molecule through a transcription factor. In that way, the DetSpace web server allows synthetic biologists to easily design biosensing routes for the dynamic regulation of metabolic pathways in applications ranging from genetic circuits design, screening, production, and bioremediation of bio-based chemicals, to diagnostics and drug delivery.

Phosphate limitation enhances malic acid production on nitrogen-rich molasses with Ustilago trichophora

BackgroundAn important step in replacing petrochemical products with sustainable, cost-effective alternatives is the use of feedstocks other than, e.g., pure glucose in the fermentative production of platform chemicals. Ustilaginaceae offer the advantages of a wide substrate spectrum and naturally produce a versatile range of value-added compounds under nitrogen limitation. A promising candidate is the dicarboxylic acid malic acid, which may be applied as an acidulant in the food industry, a chelating agent in pharmaceuticals, or in biobased polymer production. However, fermentable residue streams from the food and agricultural industry with high nitrogen content, e.g., sugar beet molasses, are unsuited for processes with Ustilaginaceae, as they result in low product yields due to high biomass and low product formation.ResultsThis study uncovers challenges in evaluating complex feedstock applicability for microbial production processes, highlighting the role of secondary substrate limitations, internal storage molecules, and incomplete assimilation of these substrates. A microliter-scale screening method with online monitoring of microbial respiration was developed using malic acid production with Ustilago trichophora on molasses as an application example. Investigation into nitrogen, phosphate, sulphate, and magnesium limitations on a defined minimal medium demonstrated successful malic acid production under nitrogen and phosphate limitation. Furthermore, a reduction of nitrogen and phosphate in the elemental composition of U. trichophora was revealed under the respective secondary substrate limitation. These adaptive changes in combination with the intricate metabolic response hinder mathematical prediction of product formation and make the presented screening methodology for complex feedstocks imperative. In the next step, the screening was transferred to a molasses-based complex medium. It was determined that the organism assimilated only 25% and 50% of the elemental nitrogen and phosphorus present in molasses, respectively. Due to the overall low content of bioavailable phosphorus in molasses, the replacement of the state-of-the-art nitrogen limitation was shown to increase malic acid production by 65%.ConclusionThe identification of phosphate as a superior secondary substrate limitation for enhanced malic acid production opens up new opportunities for the effective utilization of molasses as a more sustainable and cost-effective substrate than, e.g., pure glucose for biobased platform chemical production.

Exploiting the Thermotolerance of Clostridium Strain M1NH for Efficient Caproic Acid Fermentation from Ethanol and Acetic Acid.

A novel thermotolerant caproic acid-producing bacterial strain, Clostridium M1NH, was successfully isolated from sewage sludge. Ethanol and acetic acid at a molar ratio of 4:1 proved to be the optimal substrates, yielding a maximum caproic acid production of 3.5g/L. Clostridium M1NH exhibited remarkable tolerance to high concentrations of ethanol (up to 5% v/v), acetic acid (up to 5% w/v), and caproic acid (up to 2% w/v). The strain also demonstrated a wide pH tolerance range (pH 5.5-7.5) and an elevated temperature optimum between 35 and 40°C. Phylogenetic analysis based on 16S rRNA gene sequences revealed that Clostridium M1NH shares a 98% similarity with Clostridium luticellarii DSM 29923T. The robustness of strain M1NH and its efficient caproic acid production from low-cost substrates highlight its potential for sustainable bio-based chemical production. The maximum caproic acid yield achieved by Clostridium M1NH was 1.6-fold higher than that reported for C. kluyveri under similar fermentation conditions. This study opens new avenues for valorizing waste streams and advancing a circular economy model in the chemical industry.

Isolation of Highly Crystalline Cellulose via Combined Pretreatment/Fractionation and Extraction Procedures within a Biorefinery Concept.

Sustainable production of bio-based materials and chemicals requires integrated approaches which utilize all fractions of lignocellulosic biomass. In this work, highly crystalline cellulose was isolated via combined pretreatment/fractionation and extraction processes from beechwood sawdust. The proposed approach was based on the selective recovery of hemicellulose components in the first step, followed by enhanced delignification in the second step, permitting the efficient recovery of the remaining cellulose via bleaching in the final step. Hydrothermal pretreatment under tailored conditions in neat water or dilute acid resulted in almost complete hemicellulose removal (80-96 wt %) in the liquid fraction. In the second step, the formed surface lignin was isolated via mild extraction while enhanced removal of both native/structural and surface lignin (71 wt %) was achieved by applying the organosolv treatment using dilute sulfuric acid as catalyst. Dilute sulfuric acid pretreatment followed by acid catalyzed organosolv pretreatment proved to be the most efficient combined approach, leading to 80 wt % hemicellulose removal as xylose monomer, and 71 wt % delignification. High crystallinity cellulose (<88%), with an overall cellulose recovery of 68-91 wt % based on native cellulose in parent biomass was isolated in the last step via bleaching of all pretreated biomass solids. The proposed integrated biorefinery procedures that aim to whole "waste" biomass valorization, replacing fossil resources, with the use of green solvents (water, ethanol) at relatively mild temperature/pressure conditions, are in line with the scope of several United Nations Sustainable Development Goals, such as UN SDG 8, 11, 12, and 13.

Optimisation of the Production of Bio-Based Basic Chemicals from Biogenic Secondary Waste Through Dispersion

Biogenic waste from waste treatment plants, also known as secondary waste, can be used to produce bio-based carboxylic acids. Conventionally, these are produced by chemically synthesis of petroleum-based raw materials or synthesis of natural oils (e.g. coconut or palm kernel oil). Using organic residues and waste materials in a cascade to produce bio-based products can contribute to the circular bioeconomy. In the biological treatment process for production of bio-based carboxylic acids, microorganisms that are already present in the secondary waste use ethanol to convert short-chain carboxylic acids (with one to three carbon atoms) into medium-chain carboxylic acids (with four to ten carbon atoms). During the treatment process, medium-chain carboxylic acids are separated from the secondary waste by using in-situ extraction (liquid-liquid extraction). In previous studies, bioreactors without a dispersing function were used on a laboratory scale. In order to optimise the production and extraction of the formed medium-chain carboxylic acids, the bioreactors should be upgraded with a device for dispersing the extraction solvent in the secondary waste. Dispersing can increase the surface area between the extraction solvent and the secondary waste and therefore also the ability to extract the medium-chain carboxylic acids. To evaluate the effects of dispersing on the production of bio-based carboxylic acids, the production and extraction rates of static bioreactors without dispersing are compared with those of dynamic bioreactors with dispersing on a laboratory scale. Leachate from a composting plant was used as secondary waste. According to the results of the current study, it can be confirmed that dispersion has a positive effect on the biological treatment process. In addition to the increased degradation of the nutrient ethanol, the production of medium-chain carboxylic acids in the secondary waste as well as the extracted medium-chain carboxylic acids could be increased by dispersing.

Synthesis of sustainable chemicals and fuels from biomass derivatives using homogeneous ruthenium catalysts

This work describes the synthesis and evaluation as catalysts of two ruthenium(II) complexes, RuC1 and RuC2, containing NPN ligands=(N-(phenyl(pyridin-2-ylamino)phosphino)pyridin-2-amine and 2-((phenyl(pyridin-2-ylmethyl)phosphino)methyl)pyridine, respectively) for furfural and hydroxymethylfurfural hydrogenation. The catalysts displayed exceptional activity under mild conditions (180 °C, 40 bar H2) achieving over 98 % conversion and 98–99 % selectivity towards furfuryl alcohol (from furfural) and bis(hydroxymethyl)furan (from hydroxymethylfurfural) within 30 min, using a substrate-catalyst ratio of 3000:1. Remarkably, the catalysts maintained their efficacy even at a tenfold higher substrate loading (10,000:1), albeit with extended reaction times (3 and 4 h for furfural and hydroxymethylfurfural, respectively). Turnover frequencies (TOFs) were impressive, reaching 3920 h−1 and 3200 h−1 for furfural hydrogenation with the catalyst RuC1 and RuC2, respectively. Similarly, TOFs for hydroxymethylfurfural hydrogenation were 2450 h−1 and 2475 h−1 for RuC1 and RuC2, respectively. Notably, the catalysts exhibited excellent stability under reaction conditions. These findings demonstrate the promising potential of RuC1 and RuC2 for efficient hydrogenation of biomass-derived furans, offering a sustainable approach for the production of valuable bio-based chemicals.

Sustainability implications of the EU's bioeconomy transition along global supply chains

The EU has set ambiguous targets for the development of a bioeconomy (BE) that not only ensures sufficient production of high-quality foods but also contributes to decarbonization, green jobs and reducing import dependency through biofuels and bio-based chemical products. However, the various and complex interrelations between the BE, the natural environment as well as wider economy and society risk that the EU's targets might indirectly compromise achieving the UN Sustainable Development Goals (SDGs) globally. Here, we assess the impacts of the EU's BE on the achievement of a broad range of SDG indicators using the hybrid econometric input-output model that covers 64 countries plus a region rest of world with 36 industries and 28 agricultural production sectors each. We compare the impacts of the EU's BE across three different scenarios based on SSP2 combined with corresponding IEA and FAO scenarios describing different futures of population and GDP growth, climate policy and structural changes in the energy and agriculture sector. Our results show that, especially without further measures focusing on the circular use of biomass, the EU's BE is likely not contributing to a general improvement in SDG indicators. Instead, there are major trade-offs between various SDGs. Firstly, between the goals of climate change mitigation, on the one hand, and preservation of ecosystems through the protection of natural land, especially forests, and water bodies on the other. The second major trade-off is between the EU's goals of fostering the economic competitiveness and lowering the import dependency of fossil energy and food security especially in low income countries outside Europe.

Tolerance of hyperosmolar Candida krusei

The utilization of industrial microorganisms for the conversion of lignocellulose into high value-added chemicals is an essential pathway towards achieving carbon neutrality and promoting sustainable bioeconomy. However, the pretreated lignocellulase hydrolysate often contains various sugars, salts, phenols/aldehydes and other substances, which requires microorganisms to possess strong tolerance for direct fermentation. This study aims to investigate the tolerance of Candida krusei to substrate, salt, and high temperature shock, in order to validate its potential for utilizing the enzymatic hydrolysate of Pennisetum giganteum in seawater for fermentation. The experimental results showed that the adaptively domesticated C. krusei exhibited tolerance to glucose at a concentration of 200 g/L and became a hypertonic strain. When seawater was used instead of freshwater without sterilization, the yield of glycerol in fermentation was 109% higher than that in freshwater with sterilization. Moreover, the combined thermal shock at 32 hours of fermentation and addition of 10 Na2SO3 at 48 hours resulted in a yield of glycerol to glucose 0.37 g/g, which was 225% higher than the control group. By fermenting the enzymatic hydrolysate of P. giganteum pretreated in seawater, the total conversion rate of glucose into glycerol and ethanol reached 0.45 g/g. This study indicates that hypertonic C. krusei exhibits remarkable adaptability to substrate, salt, and temperature. It not only can directly utilize complex lignocellulosic hydrolysates, but also exhibits strong tolerance to them. Therefore, it provides a potential candidate strain for the production of bio-based chemicals using lignocellulosic processes.

Enhancing bio-based chemical production and reducing pollutants emission through the synergistic effect of ZSM-5/CaO during hydrogen-deficient biomass pyrolysis

The study proposed the use of ZSM-5/CaO as a catalyst to simultaneously improve the quality of pyrolytic products and reduce pollutants emission during the pyrolysis of hydrogen-deficient biomass, specifically cabbage waste (CW). Variables such as pyrolysis temperature and catalysts, including 5% ZSM-5, 5% CaO and 10% ZSM-5/CaO, significantly affected biomass conversion, yield, and products composition. Thermogravimetric-Fourier transform infrared spectroscopy (TG-FTIR) analysis shows that the catalysts (5% ZSM-5, 5% CaO and 10% ZSM-5/CaO) reduced pollutants emission and increased value-added chemicals production by 24.96%, 28.5%, 17.39% and 75.04%, 71.5%, 82.1%, respectively compared to non-catalytic process as 34.18% and 65.82%. Moreover, these catalysts enhanced the relative yield of olefins, aromatics, and phenols to 23.5, 21.6, 27.6% for 5wt.%ZSM-5; 20.8, 18.7, 23.3% for 5wt.%CaO; 30.7, 38.6, 41.3% for 10wt.%ZSM-5/CaO, compared to the non-catalytic process' yield of 15.7, 10.7, 19.3%. Py/GC–MS analysis confirms that these catalysts also decreased PAH and oxygenates production to 13.5, 15.3% for 5wt.%ZSM-5; 11.8, 9.1% for 5wt.%CaO; 5.2, 4.7% for 10wt.%ZSM-5/CaO, in contrast to the non-catalytic process' 26.2, 28.7%. This confirms the synergistic effect of ZSM-5/CaO for upgrading bio-based chemicals and reducing pollutants emission.