Methyl oleate for plant protection products formulations: Enzymatic synthesis, reaction kinetics and application testing.

This study presents a solvent-free enzymatic approach for the synthesis of fatty acid methyl esters (FAMEs), such as methyl oleate, for their application as adjuvant in plant protection products (PPP) formulations. The direct esterification between free fatty acid and methanol was optimized to achieve 98% acid conversion. The kinetics of this conversion was accurately described by a simple second order mechanism and non-linear regression was applied to calculate the rate constants of the forward and backward reactions based on full progress curves data. The rate constant of the forward reaction (synthesis) was one order of magnitude higher than the backward reaction (hydrolysis) and favored formation of the target methyl ester product, rendering the removal of water unnecessary. Enzymatically synthesized methyl oleate was benchmarked against the chemically synthesized compound, showing matching results in terms of stability, spreadability and emulsifying capacity in plant care formulations. The enzymatic synthesis of FAMEs under solvent free conditions allows to achieve a safer and more sustainable character for carrier solvents in PPP formulations.

Toward Renewable-Based Prebiotics from Woody Biomass: Potential of Tailored Xylo-Oligosaccharides Obtained by Enzymatic Hydrolysis of Beechwood Xylan as a Prebiotic Feed Supplement for Young Broilers.

Although antibiotic resistance emerges naturally, this process has been accelerated by the worldwide overuse and misuse of antibiotics. It is essential to find effective alternatives in the broiler industry to improve poultry health while maintaining production efficiency and product safety. In this study, we aimed to evaluate a potential alternative: wood-derived xylo-oligosaccharides (XOS). The objective of this research was to investigate the potential of XOS prepared using enzymatic hydrolysis of beechwood xylan as a prebiotic feed supplement for broilers. A pilot study was conducted to explore the optimal XOS fraction profile by in vitro fermentation. Subsequently, a semi-continuous enzyme membrane reactor was used, allowing for the production of tailored XOS in large quantities. Given the strong bidirectional relationship between intestinal health, nutrition, and intestinal microbiota composition in broilers, an in vivo experiment was performed to explore the potential of XOS as a prebiotic feed supplement by investigating growth performance, feed conversion ratio, caecal short and medium chain fatty acid (SCFA and MCFA) concentration, and microbiological composition of the caecal content. Results from the pilot study indicated that higher enzyme concentrations in the hydrolysis process yield a product that leads to a higher total SCFA and MCFA- and butyric acid production during in vitro fermentation by caecal bacteria. Supplementation of the tailored XOS to the broiler diet (day 1 (d1)-d8 0.13% wt/wt XOS, d9-d15 0.32% XOS) resulted in higher Bifidobacterium counts, beneficial to the health of birds, on d11 and d15.

Acetic acid, growth rate, and mass transfer govern shifts in CO metabolism of Clostridium autoethanogenum.

Syngas fermentation is a leading microbial process for the conversion of carbon monoxide, carbon dioxide, and hydrogen to valuable biochemicals. Clostridium autoethanogenum stands as a model organism for this process, showcasing its ability to convert syngas into ethanol industrially with simultaneous fixation of carbon and reduction of greenhouse gas emissions. A deep understanding on the metabolism of this microorganism and the influence of operational conditions on fermentation performance is key to advance the technology and enhancement of production yields. In this work, we studied the individual impact of acetic acid concentration, growth rate, and mass transfer rate on metabolic shifts, product titres, and rates in CO fermentation by C. autoethanogenum. Through continuous fermentations performed at a low mass transfer rate, we measured the production of formate in addition to acetate and ethanol. We hypothesise that low mass transfer results in low CO concentrations, leading to reduced activity of the Wood-Ljungdahl pathway and a bottleneck in formate conversion, thereby resulting in the accumulation of formate. The supplementation of the medium with exogenous acetate revealed that undissociated acetic acid concentration increases and governs ethanol yield and production rates, assumedly to counteract the inhibition by undissociated acetic acid. Since acetic acid concentration is determined by growth rate (via dilution rate), mass transfer rate, and working pH, these variables jointly determine ethanol production rates. These findings have significant implications for process optimisation as targeting an optimal undissociated acetic acid concentration can shift metabolism towards ethanol production. KEY POINTS: • Very low CO mass transfer rate leads to leaking of intermediate metabolite formate. • Undissociated acetic acid concentration governs ethanol yield on CO and productivity. • Impact of growth rate, mass transfer rate, and pH were considered jointly.

Molecular Design of Lignin-Derived Side-Chain Phenolic Polymers toward Functional Radical Scavenging Materials with Antioxidant and Antistatic Properties.

This article reports a new family of functional side-chain phenolic polymers derived from lignin monomers, displaying a combination of properties that are usually mutually exclusive within a single material. This includes a well-defined molecular structure, transparency, antioxidant activity, and antistatic properties. Our design strategy is based on the lignin-derived bioaromatic monomer dihydroconiferyl alcohol (DCA), a promising and yet largely unexplored asymmetrical diol bearing one aliphatic and one phenolic hydroxyl group. A lipase-catalyzed (meth)acrylation protocol was developed to selectively functionalize the aliphatic hydroxy group of DCA while preserving its phenolic group responsible for its radical scavenging properties. The resulting mono-(meth)acrylated monomers were then directly copolymerized using reversible addition-fragmentation chain-transfer (RAFT) polymerization without any protection of the phenolic side chains. Kinetics studies revealed that, under select conditions, these unprotected phenolic groups surprisingly did not inhibit the radical polymerization and lead to polymers with defined molar masses, low dispersities, and block copolymers. Finally, applications of these new radical scavenging polymers were demonstrated using an antioxidant assay and antistatic experiments. This research opens the door to the direct incorporation of natural antioxidants within the synthetic polymer backbones, increasing the biobased content and limiting the leaching of potentially harmful additives.

Membrane bioreactors for syngas permeation and fermentation.

Syngas fermentation to biofuels and chemicals is an emerging technology in the biobased economy. Mass transfer is usually limiting the syngas fermentation rate, due to the low aqueous solubilities of the gaseous substrates. Membrane bioreactors, as efficient gas-liquid contactors, are a promising configuration for overcoming this gas-to-liquid mass transfer limitation, so that sufficient productivity can be achieved. We summarize the published performances of these reactors. Moreover, we highlight numerous parameters settings that need to be used for the enhancement of membrane bioreactor performance. To facilitate this enhancement, we relate mass transfer and other performance indicators to the type of membrane material, module, and flow configuration. Hollow fiber modules with dense or asymmetric membranes on which biofilm might form seem suitable. A model-based approach is advocated to optimize their performance.

Effects of moderately elevated pressure on gas fermentation processes.

Industrial biotechnology has a potential to tackle harmful CO2 emissions and turn CO2 into a valuable commodity. However, a major technical obstacle in gas fermentations is the limited gas mass transfer rate. Increasing system pressure is a way to increase the driving force for mass transfer. This review presents critical aspects of gas fermentation at elevated pressure, with a specific focus on results obtained at 5-10 bar. While a solid foundation for high pressure fermentations has already been laid in the past, mainly to enhance oxygen transfer rates, it can be concluded that fermentations at moderately elevated pressures using gases such as CO2, CH4, CO, H2, O2 are still underexplored. Microbial growth rates and product formation can be improved at higher pressures, but in general, titers and productivities need to be increased to allow a further industrialization. Hence, more systematic investigations and techno-economic assessments are required.

Biobutanol production from C5/C6 carbohydrates integrated with pervaporation: experimental results and conceptual plant design.

In this study, a simulated lignocellulosic hydrolyzate was used in a continuous two-stage fermentor setup for production of acetone, butanol and ethanol. An organophilic pervaporation unit was coupled to the second fermentor. The dilution rate in the first fermentor was kept constant at 0.109 h(-1), while the dilution rate in the second fermentor was gradually decreased from 0.056 to 0.020 h(-1). Glucose was completely consumed, while 61% of the xylose was consumed at the lowest dilution rate, leading to an overall solvent productivity of 0.65 g L(-1) h(-1) and a high concentration of 185 g kg(-1) solvents in the permeate in the last fermentation zone during 192 h. Based on the experimental results, a process integrated with organophilic pervaporation was conceptually designed and compared with a base-case. Chemcad simulations indicate an energy reduction of ~50% when organophilic pervaporation is used. This study also demonstrates significant reductions in process flows and energy consumption by the use of organophilic pervaporation as in situ product recovery technology.

Advances in in-situ product recovery (ISPR) in whole cell biotechnology during the last decade.

The review presents the state-of-the-art in the applications of in-situ product recovery (ISPR) in whole-cell biotechnology over the last 10years. It summarizes various ISPR-integrated fermentation processes for the production of a wide spectrum of bio-based products. A critical assessment of the performance of various ISPR concepts with respect to the degree of product enrichment, improved productivity, reduced process flows and increased yields is provided. Requirements to allow a successful industrial implementation of ISPR are also discussed. Finally, supporting technologies such as online monitoring, mathematical modeling and use of recombinant microorganisms with ISPR are presented.

Pervaporative recovery of ABE during continuous cultivation: enhancement of performance.

Acetone, butanol and ethanol were produced in a continuous two-stage fermentation integrated with pervaporation using freely suspended cells of C. acetobutylicum ATCC 824. PDMS composite pervaporation membranes were directly coupled to the second fermentor which lead to decreased solvent titers. Overall productivity was increased from 0.45 g L(-1) h(-1) to 0.88 g L(-1) h(-1) when increasing the carbohydrate concentration in the feed from 60 to 120 g L(-1). The highest overall productivity of 1.13 g L(-1) h(-1) was achieved when increasing the carbohydrate concentration further to 150 g L(-1) even though productivity decreased significantly in the first fermentor due to substrate inhibition. In this phase that lasted 200 h, the average flux reached 0.621 kg m(-2) h(-1) and the total solvent concentration in the permeate was 202 g L(-1). High solvent titers in the second fermentor were beneficial for the performance of the pervaporation unit leading to higher fluxes and total solvent concentrations in the permeate.

Integrated bioprocess for long-term continuous cultivation of Clostridium acetobutylicum coupled to pervaporation with PDMS composite membranes.

A continuous cultivation of Clostridium acetobutylicum ATCC 824 is described using a two-stage design to mimic the two phases of batch culture growth of the organism. A hydrophobic pervaporation unit was coupled to the second fermentor containing the highest solvent titers. This in situ product recovery technology efficiently decreased butanol toxicity in the fermentor while the permeate was enriched to 57-195 g L(-1) total solvents depending on the solvent concentrations in the fermentor. By the alleviation of product inhibition, the glucose concentration could be increased from 60 to 126 g L(-1) while the productivity increased concomitantly from 0.13 to 0.30 g L(-1)h(-1). The continuous fermentation was conducted for 1172 h during which the pervaporation was coupled to the second fermentor for 475 h with an average flux of 367 g m(-2)h(-1). The energy consumption was calculated for a 2 wt.% n-butanol fermentation broth and compared with the conventional process.

Biocatalytic cascade oxidation using laccase for pyranose 2-oxidase regeneration.

The interactions between two oxidoreductases coupled by an artificial redox mediator have been described quantitatively to increase both stability and productivity. In this cascade oxidation, pyranose 2-oxidase oxidizes several aldoses at the C-2 position to 2-ketoaldoses. A redox mediator is used as electron acceptor for pyranose 2-oxidase because it shows more favourable kinetics in comparison to oxygen. The reduced redox mediator is in turn re-oxidized by laccase, which uses oxygen as the terminal electron acceptor, reducing it fully to water. However, pyranose 2-oxidase is capable of using oxygen as an electron acceptor in a competing side reaction, leading to the formation of hydrogen peroxide, which is detrimental for both enzymes and seriously limits the operational stability of both enzymes. The experimental results showed full conversion of the aldose to the 2-ketoaldose and a good agreement with the simulations of the process.

Kinetic modeling of a bi-enzymatic system for efficient conversion of lactose to lactobionic acid.

A model has been developed to describe the interaction between two enzymes and an intermediary redox mediator. In this bi-enzymatic process, the enzyme cellobiose dehydrogenase oxidizes lactose at the C-1 position of the reducing sugar moiety to lactobionolactone, which spontaneously hydrolyzes to lactobionic acid. 2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt is used as electron acceptor and is continuously regenerated by laccase. Oxygen is the terminal electron acceptor and is fully reduced to water by laccase, a copper-containing oxidase. Oxygen is added to the system by means of bubble-free oxygenation. Using the model, the productivity of the process is investigated by simultaneous solution of the rate equations for varying enzyme quantities and redox mediator concentrations, solved with the aid of a numerical solution. The isocharts developed in this work provide an easy-to-use graphical tool to determine optimal process conditions. The model allows the optimization of the employed activities of the two enzymes and the redox mediator concentration for a given overall oxygen mass transfer coefficient by using the isocharts. Model predictions are well in agreement with the experimental data.

Bubble-free oxygenation of a bi-enzymatic system: effect on biocatalyst stability.

The effect of bubble-free oxygenation on the stability of a bi-enzymatic system with redox mediator regeneration for the conversion of lactose to lactobionic acid was investigated in a miniaturized reactor with bubbleless oxygenation. Earlier investigations of this biocatalytic oxidation have shown that the dispersive addition of oxygen can cause significant enzyme inactivation. In the process studied, the enzyme cellobiose dehydrogenase (CDH) oxidizes lactose at the C-1 position of the reducing sugar moiety to lactobionolactone, which spontaneously hydrolyzes to lactobionic acid. 2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt was used as electron acceptor for CDH and was continuously regenerated (reoxidized) by laccase, a blue multi-copper oxidase. Oxygen served as the terminal electron acceptor of the reaction and was fully reduced to water by laccase. The overall mass transfer coefficient of the miniaturized reactor was determined at 30 and 45 degrees C; conversions were conducted both in the reaction-limited and diffusion-limited regime to study catalyst inactivation. The bubbleless oxygenation was successful in avoiding gas/liquid interface inactivation. It was also shown that the oxidized redox mediator plays a key role in the inactivation mechanism of the biocatalysts unobserved during previous studies.