Acid Yield Research Articles

Optimization of Aerobic Synthesis of Fumaric Acid from Glucose by a Recombinant Escherichia coli Strain Functioning in a Whole-Cell Biocatalyst Mode

Biocatalytic synthesis of fumaric acid from glucose by the previously engineered E. coli strain FUM1.0 (pMW119-kgd) (E. coli MG1655 ∆ackA-pta, ∆ldhA, ∆adhE, ∆ptsG, PL-glk, Ptac-galP, ∆fumB, ∆fumAC, poxB::PL-pycABs, pMW119-kgd) was optimized. The maximal yield of the target substance was achieved upon its synthesis through a variant of the tricarboxylic acid cycle mediated by the action of heterologous 2-ketoglutarate decarboxylase. The enhanced expression of the genes encoding components of the succinate dehydrogenase enzymatic complex did not markedly affect the biosynthetic characteristics of the producing strain. A positive effect of decreasing the intracellular ATP supply on the conversion of the carbohydrate substrate into the target product was demonstrated. The activation of the futile cycle of pyruvate–phosphoenolpyruvate–pyruvate due to an increase in the expression of the ppsA gene led to a slight increase in the yield of fumaric acid. Upon uncoupling the H+-ATP synthase complex subunits resulting in ATP formation cessation via oxidative phosphorylation, due to deletion of the atpFH genes, the molar yield of fumaric acid from glucose demonstrated by the strain functioning in the whole-cell biocatalyst mode reached 92%.

Optimisation of coumaric acid production from aromatic amino acids in Kluyveromyces marxianus

Yeasts are attractive hosts for the production of heterologous products due to their genetic tractability and relative ease of growth. While the baker’s yeast Saccharomyces cerevisiae is a powerful workhorse of the biotechnology industry, the species has metabolic limitations and it is critical that we develop alternative platforms that will facilitate the development of bioprocesses that rely on sustainable feedstocks. In this study, we used synthetic biology tools to construct coumaric acid–producing strains of Kluyveromyces marxianus, a yeast whose physiological traits render it attractive for biotechnology applications. Coumaric acid is a building block in the synthesis of many different families of aromatics and is a key precursor for the synthesis of complect phenylpropanoid molecules, including many flavours and aromas. The starting point for this work was a K. marxianus chassis strain that has increased flux towards the synthesis of tyrosine and phenylalanine, the aromatic amino acids that can serve as starting points for coumaric acid synthesis. Following principles of synthetic biology, a modular approach was taken to identify the best solution to different metabolic possibilities and these were then combined in different ways. For the first step, it was established that the route from phenylalanine was superior to that from tyrosine and the combined overexpression of PlPAL, AtC4H and AtCPR1 delivered the highest yield of coumaric acid. Next, it was established that while Pdc5 and Aro10 both had phenylpyruvate decarboxylase activity, inactivation of ARO10 was sufficient to prevent flux loss in the pathway. Since phenylalanine is the starting point, efforts were made to improve efficiency of its production. It was found that glutamate was a preferred nitrogen source for coumaric acid production, and this knowledge was used to engineer a strain that overexpressed S. cerevisiae GDH1 and delivered higher yields of coumaric acid. Ultimately, this strategy led to the development of strains that has yields of up to 48mg coumaric acid /g glucose. Strains were evaluated in bioreactors to investigate the effects of different process parameters. These analyses indicated that engineered strains face some redox balance challenges and further work will be required overcome these to develop strains that can perform well under industrial conditions.

A synergistic fermentation system of probiotics with low-cost and high butyric acid production: Lactiplantibacillus plantarum and Clostridium tyrobutyricum

Butyric acid plays a significant role in maintaining body health, and thus the research on cost-effective and efficient biological conversion strategies for butyric acid production holds great importance. This study utilized the mutual interactions between prebiotics and multiple probiotic strains to target increasing the butyric acid yield in a co-fermentation system. Briefly, xylan, an inexpensive biomass material, was used as a prebiotic to screen lactic acid bacteria that capable of being promoted for proliferation and metabolism in its presence. Subsequently, the interaction between the screened lactic acid bacteria and a butyric acid-producing strain (Clostridium tyrobutyricum) was utilized to enhance butyric acid production. The results showed that xylan significantly improved the proliferation and lactic acid metabolizing ability of Lactiplantibacillus plantarum C0502. Whole-genome analysis revealed that L. plantarum carries at least four distinct enzyme genes related to the hydrolysis and utilization of xylan. Co-cultivation of L. plantarum with C. tyrobutyricum demonstrated that the C. tyrobutyricum was able to effectively convert lactic and acetic acids into butyric acid. Furthermore, the addition of xylan into this co-culture system yielded a remarkable butyric acid production of up to 5.01 ± 0.04 g/L, which is 4.58 times higher than the yield obtained from the monoculture of C. tyrobutyricum in reinforced Clostridium medium. The results of this study suggested that the co-culture system of xylan, L. plantarum, and C. tyrobutyricum has the potential to significantly enhance butyric acid production while markedly reduce the production cost. This has immense prospects for practical applications.

Advanced in the Production of L-Ascorbic Acid using Biotechnological Processes

Over the past decade there has been increasing demand to develop alternatives to the Reichstein process, a largely chemical synthesis by which the majority of vitamin C (L-ascorbic acid) is produced. Many studies improve the biotransformation of Reichstein intermediate, but no natural bacterial strain is capable of catalyzing the biosynthesis of intermediates in single step fermentation. The study aimed to Isolate and identify bacterial strains have the ability to produce Ascorbic acid and detect their ability to be cultivated on plant wastes as substrate. In this study a total of Seventy-five different bacterial colonies of acetic acid bacteria were isolated from eight different samples. The most potent isolate was identified by 16S rRNA and phylogenetic tree relationship showed that the isolated strain was novel and named Gluconobacter oxydans st SW with accession number OP429626. The optimal levels of different nutritional and cultural variables were reached. The data revealed that the yield of ascorbic acid was increased from 7.17 g/l to 10.348 g/l. The effect of low doses of gamma radiation was tested. For Gluconobacter oxydans st. SW, the highest ascorbic acid yield was obtained was 20.480 g/l at activation radiation dose 1.2 kGy compared with 10.34 g/l from the parent isolate at the optimum fermentation conditions. It was observed that the radiated Gluconobacter oxydans st SW can adapt to the waste’s hydrolysate more than the un-radiated one. The highest yield of ascorbic acid (21.2 g/l) was obtained from fermentation broth containing 70% supplemented hydrolsate and 30% synthetic fermentation broth.

Boosting CO2 photoreduction to acetic acid via the van der waals heterostructures of monolayer Nb2O5 modified TiO2 nanotubes

Photoreduction of CO2 to hydrocarbons encounters two significant challenges: low product yields and poor selectivity. Furthermore, the difficulty of C-C coupling reactions hinders the formation of higher-value two-carbon products. This paper presents a strategy to address these challenges by fabricating a van der Waals heterostructure photocatalyst through the surface modification of TiO2 nanotubes (TNTs) with monolayer Nb2O5, denoted as 3 %Nb2O5/TNTs. Compared with TNTs, the acetic acid yield of heterostructures reached 28.4 μmol gcat-1h−1, and the selectivity rose from 48 % to 69 %. The van der Waals heterostructures reduced the photogenerated electron-hole recombination, extending the lifetime of charge carriers. The reduction of resistance and the presence of built-in fields accelerated the migration of charge carriers, thereby showing an enhanced photocatalytic performance. Surface modification of monolayer Nb2O5 promoted the activation adsorption of CO2 to CO2·-, facilitating the following C-C coupling reaction. Furthermore, its surface acidity sites modulated the hydrogenation reactions following C-C coupling, thereby increasing both the yield and selectivity of acetic acid.

Using process modeling and simulation to determine the sustainability of a novel lactic acid biorefinery in Europe: Influence of process improvements, scale, energy source, and market conditions

The biorefinery concept aims to produce multiple high-value products from bio-based feedstocks. One such product is lactic acid, which is used across several industries such as food, pharmaceuticals, cosmetics, and chemicals. Lactic acid yield is influenced by several factors, and improvements in performance are often first demonstrated at lab-scale, requiring prospective models which make assumptions about how the system will be optimized to understand the potential of a commercial-scale plant. This study assesses the economic and environmental sustainability of a proposed lactic acid biorefinery through the combination of process modelling, techno-economic assessment, and life cycle assessment. The case study proposes producing high purity lactic acid from industrial candy waste and liquid digestate in Denmark through lactic acid fermentation and downstream membrane separations. A base case is first modelled to determine the economic and environmental hotspots of the system; scenarios are then modelled where improvement methods are implemented reducing consumption of energy, chemicals, water, and the production of waste, upscaling the system, and integrating bioenergy. Finally, a cost sensitivity analysis is run varying bioenergy, water, chemical, and labor costs based on the European market. By optimizing unit processes, scale, energy sources and market conditions, the lactic acid unit production cost and global warming potential can be lowered by 94% and 80% compared to the base case, respectively. However, these are optimized in different scenarios, indicating a trade-off in optimizing economic and environmental criteria. As even best-case lactic acid unit production cost is found to be 141–232% higher than market price, this production pathway will require further improvement or market changes before it can be commercially viable.

A hybrid in silico/in-cell controller that handles process-model mismatches using intracellular biosensing

The discrepancy between model predictions and actual processes, known as process-model mismatch (PMM), remains a substantial challenge in bioprocess optimization. We previously introduced a hybrid in silico/in-cell controller (HISICC) that combines model-based optimization with cell-based feedback to address this problem. Here, we extended this approach to regulate a key enzyme level using intracellular biosensing. The extended HISICC was implemented using an Escherichia coli strain engineered for fatty acid production (FA3). This strain contains a genetically encoded feedback controller that decelerates the expression of acetyl-CoA carboxylase (ACC) in response to malonyl-CoA synthesized through the enzymatic reaction. We modeled FA3 to allow the HISICC to optimize an inducer input that accelerates the enzyme expression. Simulations showed that the HISICC slowed the unexpectedly rapid accumulation of ACC resulting from PMMs before it reached cytotoxic levels, thereby improving fatty acid yields. These results highlight the potential of our approach, particularly in cases where monitoring intracellular biomolecules is required to handle PMMs.

Effect of aluminum nanoparticles size and concentration on the combustion characteristics of nanofluid fuel: Experiments and modeling

Nanofluid fuel has garnered significant attention due to its potential to enhance combustion characteristics, energy density, and ignition properties. The study comprehensively examined the effects of aluminum nanoparticles with diverse sizes (50 nm, 100 nm, 200 nm, 500 nm, 1 μm) and concentrations (2.5 wt%, 5.0 wt%, 7.5 wt%) on the ignition and combustion characteristics of nanofluid fuel droplets, utilizing a mechanically mixed aluminum-based nanofluid fuel solution that incorporated kerosene, aluminum particles, and the surfactant oleic acid. The combustion process of the nanofluid fuel droplets encompasses phases of ignition, steady combustion, micro-explosion, and agglomerate reaction. The surface temperature of the nanofluid fuel droplets consistently exceeded that of a pure kerosene droplet, with temperature elevations correlating positively with particle concentration but not with the particle size. The surface temperature of nanofluid fuel droplets containing 7.5 wt% aluminum particles is approximately 205°C. The incorporation of oleic acid into pure kerosene prolongs the ignition delay from 0.317 s to 0.333 s. The combustion rate of the nanofluid fuel droplets escalates upon the addition of aluminum particles, with the rate escalating in tandem with the diameter and concentration of the aluminum particles. Nanofluid fuel droplets containing 5.0 wt% aluminum and 5.0 wt% oleic acid particles exhibit a combustion rate akin to that of pure kerosene droplets, with rates of 0.596 and 0.604 mm2 s−1, respectively. Concurrently, the ignition delay for nanofluid fuel droplets is longer than that of pure kerosene, yet it exhibits insensitivity to particle size. The ignition delay for nanofluid fuel droplets with the addition of 7.5 wt% aluminum particles is approximately 1.5 times that of kerosene. Nanofluid fuel droplets devoid of oleic acid yield divergent results due to particle agglomeration effects. Subsequently, as particle size increased, the surface of combustion residue develops more pronounced bulges, becoming more prone to rupture. Ultimately, a kinetic prediction model is proposed, accounting for the inhomogeneous properties within the droplet. The root mean squared errors for ignition delay time, combustion rate, and steady surface temperature are all below 8 %, indicating a strong correlation between model predictions and experimental data. This research could help accelerate the adoption of aluminum-based nanofluid fuel.

Products Distribution and Reaction Kinetics from Co-Pyrolysis of Pinewood and Polypropylene under Non-Catalytic and Catalytic Reaction Conditions

Abstract Co-pyrolysis technology offers vital pathways for efficient utilization of plastics and biomass resources to help reduce the environmental problems and energy resources issues. The pyrolysis characteristics of pinewood and polypropylene (PP) mixtures were analyzed using TGA. The results showed a decrease in first peak of the mixture with increase in PP in the mixture, while the second peak increased with an increase in PP in the mixture. The addition of a catalyst decreased the DTG peak heights. The reduction in the first peak with different catalysts was in the order: CaO/ZSM-5 >CaO >ZSM-5, while for the second peak showed: CaO >CaO/ZSM-5 >ZSM-5. The activation energy, calculated by Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), and Friedman models, revealed that ZSM-5 reduced the activation energy, whereas CaO/ZSM-5 increased the activation energy, as compared to no catalyst case. Increase of co-pyrolysis temperature reduced the yield of aldehydes, ketones, acids and esters, but increased the yield of hydrocarbons. The addition of CaO reduced the yield of ketones, phenols, esters, and acids, while it increased the yield of alcohols. The addition of ZSM-5 also decreased the yield of ketones, phenols, acids and hydrocarbons, but increased the yield of furans and alcohols. The addition of CaO/ZSM-5 specifically reduced the yield of aldehydes and alcohols. The results show the important role of the specific catalysts examined on the resulting products distribution for the same reaction condition.

Development of a non-targeted metabolomics-based screening method for elucidating the metabolic characteristics and potential applications of Lacticaseibacillus paracasei

The increasing demand for healthy foods has led to widespread interest in lactic acid bacteria due to their potential health benefits. We propose the hypothesis that Lacticaseibacillus paracasei (L. paracasei) can produce beneficial metabolites under specific conditions, which offers potential applications in functional foods. In this study, we analyzed the fermentation supernatants and brown fermented milk metabolites of L. paracasei to identify those with possible applications in functional foods, which have great potential. We found that L. paracasei IMAU32642 produced unique metabolites, including docosahexaenoic acid (DHA), leucyl phenylalanine, and oleic acid in its fermentation supernatant. Meanwhile, L. paracasei IMAU60048 exhibited unique application prospects in brown fermented milk, with higher yields of arachidonic acid and caprylic acid compared to other strains. This study offers a new and effective method for screening L. paracasei. The study can promote the development of functional foods and enhance their health value.

Evaluating rice lipid content, yield, and quality in response to nitrogen application rate and planting density.

To investigate the effects of nitrogen (N) application rate and planting density (D) on the contents of lipid and free fatty acid, fatty acid composition, yield and quality of rice grain, a field experiment was conducted using Koshihikari (japonica) as experimental material from 2021 to 2022 with three N levels (90, 150 and 210 kg ha-1, denoted as N1, N2 and N3, respectively) and three transplanting densities (19.0 × 104, 26.7 × 104 and 40.0 × 104 plants ha-1, denoted as D1, D2 and D3, respectively). The results showed that N application rate and planting density had highly significant impacts only on the contents of free fatty acid and saturated fatty acid, respectively. Increased N and planting density enhanced the contents of lipid (29.41 mg g-1) and free fatty acid (21.47%). The highest values were obtained under N3D3 increasing by 7.02% and 3.23 percentage points, respectively, compared to other treatments. No significant differences in lipid content were found among treatments, whereas free fatty acid exhibited significant differences. The unsaturated fatty acid content increased with increasing N but first decreased and then increased with increasing planting density, while saturated fatty acid content showed the opposite trend. Appropriate N level and planting density improved the relative chlorophyll content and net photosynthetic rate of rice flag leaves, as well as increased grain yield, effective panicle number and spikelete number per panicle, but decreased the seed setting rate. Under N2D2, the relative chlorophyll content and net photosynthetic rate remained relatively high throughout the grain filling stage, resulting in the highest grain yield, with increases of 43.87-47.03% compared to other treatments. Amoderate N level improved the milling quality of rice, while increased planting density reduced it. However, both increased N and planting density reduced the appearance quality and cooking and eating quality of rice. Overall, the effects of increasing N application rate and planting density on enhancing rice lipid and free fatty acid contents were limited. A combination of 150 kg ha-1 N application rate and 26.7 × 104 plants ha-1 was recommended for achieving relatively higher yield, lipid content and better grain quality.

Metabolic Dynamics Of Bacterial Strains In Eichhornia crassipes Hydrolysate: A Comparative Study Of Growth And Lactic Acid Production

In the present investigation, the growth conditions in a fermentation process at 35 °C, 180 rpm for 60 h, of four strains of commercial bacteria DRI SET 432, DRI FAS 992, Bacillus subtilis, and water kefir were compared in two growth media (M1 base growth medium and M2 medium supplemented with E. crassipes hydrolysate). The metabolic response of the strains in the media was monitored and evaluated by means of biomass production by the Mc Farland turbidimetric method (cells.mL-1), sugar consumption (g.L-1) DNS method and lactic acid production (%) NTC 4978, these controls were performed every 12 h. The strains evaluated presented their growth phase in the growth media. The strains evaluated presented their exponential phase at 12 h in M1 and M2. We found a decrease in biomass and lactic acid production in the fermentation processes with M2 for DRI SET 432, DRI FAS 992 and water kefir, and a greater growth with Bacillus subtilis (32 x 108 cells/mL) at 60 h. On the other hand, the highest lactic acid yield was presented with strain FAS 992 (streptococcus salivarius sub. thermophilus) with 1.390 g lactic acid/ g substrate consumed in M1 and in Water kefir with 0.753 g lactic acid/ g substrate consumed for M2.

Quantitative Analysis of Lactobionic Acid in Bioreactor Cultures and Selected Biological Activities.

The aim of this study was to quantitatively analyse lactobionic acid obtained from bioreactor cultures using whey as a liquid medium with bacteria of the Pseudomonas taetrolens species. The most important culture parameters affecting the production of the acid are indicated and evaluated. The highest lactobionic acid yield was 37.42 g/L, selecting the appropriate strain (Pseudomonas taetrolens 4') and environmental conditions (2% lactose concentration in the bioreactor). The amount of lactose and lactobionic acid was determined by high-performance liquid chromatography. Microorganism analysis was also carried out using a flow cytometer with imaging to study the metabolic activity of microorganisms during lactobionic acid production. In addition, during the study, Bifidobacteria were microencapsulated with lactobionic acid and their survival was evaluated in an in vitro model of the gastrointestinal tract, checking the prebiotic properties of the acid. The highest number of viable cells in the microcapsules after digestion was obtained using the Bifidobacterium bifidum strain DSM 20082. The antagonistic activity of lactobionic acid was also analysed.

Synergistic enhancement of nickel-cobalt nano-catalysts for 5-hydroxymethylfurfural conversion via electronic structure engineering and solar intensification

The electrooxidation of 5-hydroxymethylfurfural (HMF) into vital chemical intermediates has received widespread attention. In order to achieve efficient conversion of HMF, the main focus has been on the design and development of delicate catalysts. In addition, the introduction of an external field in the reaction process can also improve the electrocatalytic efficiency. In this paper, nickel-cobalt composite oxide catalysts with controlled metal centers (Ni/Co) were synthesized by a simple “coating-calcination” method. The rational rearrangement of d-electron by Co-doping facilitated the improvement of HMF adsorption, which was further confirmed by Density Functional Theory calculations. The catalysts synthesized at the optimal Co-doping ratio could still achieve 100 % of HMF conversion, 95.65 % of 2,5-furandicarboxylic acid yield, and 92.97 % of Faraday efficiency after 25 electrochemical cycles. Crucially, we introduced solar illumination to further enhance the performance of electrooxidation HMF. The catalyst performance was further improved via local photothermal effect and additional photocurrent. Therefore, the yield of FDCA was increased by more than 27 % under 2.0 kW m−2 illuminations. An electrooxidation system constructed based on external field enhancement and catalyst design provides new insights into the efficient conversion of biomass.

Development of an eco-fractionation process for Ricinodendron heudelotii oil to obtain α-eleostearic acid and β-eleostearic acid

Abstract The present article studies the transformations and fractionation of the reserve lipids of Ricinodendron heudelotii. The native triglycerides of this oil are composed mainly of conjugated polyunsaturated fatty acids, in particular α-eleostearic acid C18:3 n– 5 (9c, 11t, 13t) at 60%. This particular fatty acid of CLnA family exerts many activities potentially beneficial for health: anti-inflammatory, anti-leukemic, anti-microbial, anti-tumor, anti-ulcer and anti-diabetic. A process for transforming this acid into its isomers β-eleostearic acid and catalpic acid was explored with the aim of obtaining fractions enriched in β-eleostearic acid C18:3 n– 5 (9t, 11t, 13t). The β-eleostearic acid is a fatty acid of great interest because it is even more reactive and more efficient as antioxidant than α-eleostearic acid due to its higher trans content. Isomerization reaction of α-eleostearic acid in oil was carried out using artificial solar radiation treatment. The enrichment of concentrates in β-eleostearic acid was therefore tested using an eco-fractionation process. This process was carried out in two stages. The first step was the Candida rugosa lipase-catalyzed hydrolysis of triglycerides from native or isomerized Ricinodendron heudelotii oil. The second step was fractionation of the reaction medium obtained after hydrolysis. Triglyceride hydrolysis was complete, with a yield of free fatty acids of over 95% after 2 h of reaction. Treatment of the reaction media yielded 3 lipid concentrates with new chemical compositions of polyunsaturated fatty acids: a first concentrate, derived from hydrolysis of the native oil, composed of 60% α-eleostearic acid and 22% linoleic acid, and two other concentrates derived from fractionation of the hydrolysate of the oil isomerized by radiation. One was composed of 34% linoleic acid, 21% β-eleostearic acid, 11% α-eleostearic acid and 6% catalpic acid, and the last concentrate was composed of over 80% β-eleostearic acid. In addition to offering nutritional benefits similar to those of α-eleostearic acid, β-eleostearic acid also offers an interesting physical property: a very high melting point of 72 °C. Such a polyunsaturated fatty acid, which is solid at room temperature, could prove to be a raw material of choice, particularly in the world of food formulation, where manufacturers are looking for replacements with physical properties close to those of palm oil (the melting point of palmitic acid is 62 °C). Ricinodendron heudelotii oil has thus demonstrated its major role as a source of the triptych of α-eleostearic, β-eleostearic and linoleic fatty acids.

CRYSTALLIZATION TEMPERATURE AND SOLVENT COMPOSITION EFFECT FOR ENHANCEMENT OF UNSATURATED FATTY ACIDS FROM PALM OIL USING UREA COMPLEXATION

Mono and Poly Unsaturated Fatty Acids (MUFAs/PUFAs) are vital nutritional sources for infants, adults, and the elderly. The content of monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs) can be enhanced in vegetable oils or animal fats using a range of different techniques. The process of urea complexation is highly effective and efficient for concentrating monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs) from vegetable oils. This study employed refined palm oil as the raw material that went through saponification and purification processes in order to generate fatty acids mixture. Subsequently, urea was introduced to create a complex chemical in the form of urea complexed fraction (UCF) and leaving the non-urea complexed fraction (NUCF). Gas chromatography was employed to analyze the fatty acid composition obtained from urea complexation. This study investigated the impact of different crystallization temperatures (-4°C, 8°C, 12°C, 22°C, and 30°C) and ethanol concentrations (ranging from 0% to 100%) on enhancing the unsaturated content and yield of fatty acids derived from palm oil. It also conducted predictive equations to determine the yield and fatty acids composition in the non-urea complexed fraction (NUCF) which are important for separation process design in chemical industries. The study revealed that increasing the crystallization temperature resulted in a larger yield in the liquid fraction (NUCF), but a lower concentration of monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs).

Simple enzymatic depolymerization process based on rapid ball milling pretreatment for high-crystalline polyethylene terephthalate fibers

The high crystallinity (30 %–50 %) of discarded polyester textile waste limits the industrialization of its clean enzymatic depolymerization. In this study, a simple process based on ball milling pretreatment was developed to achieve effective enzymatic hydrolysis of high-crystalline polyester fiber. Ball milling was selected for its short, mild, and chemical-free process, which achieved a remarkable 23.8-fold (60.9 %) increase in terephthalic acid (TPA) yield from waste polyethylene terephthalate (PET) degradation, along with high TPA purity in the released soluble compounds. Just 30 min of ball milling at room temperature induced polyester amorphization, resulting in polyester with 12 % lower crystallinity compared with untreated polyester (51 %), while simultaneously increasing the surface roughness of polyester, thereby enhancing the efficiency of enzymatic hydrolysis. The simple process for effective enzymatic-depolymerization of waste polyester fiber developed in this study has potential industrial applications.

In-Situ Product Removal for the Enzymatic Depolymerization of Poly(ethylene terephthalate) via a Membrane Reactor.

Poly(ethylene terephthalate) (PET) is a common single-use plastic and a major contributor to plastic waste. PET upcycling through enzymatic depolymerization has drawn significant interests, but lack of robust enzymes in acidic environments remains a challenge. This study investigates in-situ product removal (ISPR) of protons and monomers from enzymatic PET depolymerization via a membrane reactor, focusing on the ICCG variant of leaf branch compost cutinase. More than two-fold improvements in overall PET depolymerization and terephthalic acid yields were achieved employing ISPR for an initial PET loading of 10 mgPET mlbuffer -1. The benefit of ISPR was reduced for a lower initial loading of 1 mgPET mlbuffer -1 due to decreased need for pH stabilization of the enzyme-containing solutions. A back-of-envelop analysis suggests that at a modest dilution ratio, ISPR could help achieve savings on caustic base solutions used for pH control in a bioreactor. Our study provides valuable insights for future ISPR developments for enzymatic PET depolymerization, addressing the pressing need for more sustainable solutions towards plastic recycling and environmental conservation.

Customising Sustainable Bio-Based Polyelectrolytes: Introduction of Charged and Hydrophobic Groups in Cellulose.

Cellulose has been widely explored as a sustainable alternative to synthetic polymers in industrial applications, thanks to its advantageous properties. The introduction of chemical modifications on cellulose structure, focusing on cationic and hydrophobic modifications, can enhance its functionality and expand the range of applications. In the present work, cationization was carried out through a two-step process involving sodium periodate oxidation followed by a reaction with the Girard T reagent, yielding a degree of substitution for cationic groups (DScationic) between 0.3 and 1.8. Hydrophobic modification was achieved via esterification with fatty acids derived from commercial plant oils, using an enzyme-assisted, environmentally friendly method. Lipase-catalysed hydrolysis, optimised at 0.25% enzyme concentration and with a 1 h reaction time, produced an 84% yield of fatty acids, confirmed by FTIR and NMR analyses. The degree of substitution for hydrophobic groups (DShydrophobic) ranged from 0.09 to 0.66. The molecular weight (MW) of the modified cellulose derivatives varied from 1.8 to 141 kDa. This dual modification strategy enables the creation of cellulose-based polymers with controlled electrostatic and hydrophobic characteristics, customisable for specific industrial applications. Our approach presents a sustainable and flexible solution for developing cellulose derivatives tailored to diverse industrial needs.

Improvements in the manufacture of benzoic acid obtained by catalytic oxidation of toluene

This study investigates improvements in benzoic acid production through the catalytic oxidation of toluene with cobalt octoate. The oxidation process, which occurs under controlled conditions with temperatures ranging from 130 °C to 165 °C, typically results in a conversion rate of 50% toluene with a selectivity of 80% over benzoic acid. However, various by-products such as benzyl alcohol, benzaldehyde, and benzyl benzoate are also formed, which reduces the overall yield. The work identifies methods to minimize these byproducts, particularly benzyl benzoate, which forms in the distillation column. One strategy investigated involved using additives to inhibit the esterification reaction that produces benzyl benzoate, aiming to improve the selectivity of the oxidation process. Experimental results show that maintaining reaction temperatures between 135 °C and 145 °C in combination with using sodium benzoate as an additive effectively reduces the formation of benzyl benzoate and increases the yield of benzoic acid. Furthermore, increasing the O2/toluene ratio increases the oxidation efficiency.