Kinetic, oxygen mass transfer and hydrodynamic studies in a three-phase stirred tank bioreactor for the bioconversion of (+)-valencene on Yarrowia lipolytica 2.2ab

CFD evaluation of hydrophobic feedstock bench-scale fermenters for efficient high agitation volumetric mass transfer

A new biomanufacturing platform combining intracellular metabolic engineering of the oleaginous yeast Yarrowia lipolytica and extracellular bioreaction engineering provides efficient bioconversion of plant oils/animal fats into high-value products. However, predicting the hydrodynamics and mass transfer parameters is difficult due to the high agitation and sparging required to create dispersed oil droplets in an aqueous medium for efficient yeast fermentation. In the current study, commercial computational fluid dynamic (CFD) solver Ansys CFX coupled with the MUSIG model first predicts two-phase system (oil/water and air/water) mixing dynamics and their particle size distributions. Then, a three-phase model (oil, air, and water) utilizing dispersed air bubbles and a polydispersed oil phase was implemented to explore fermenter mixing, gas dispersion efficiency, and volumetric mass transfer coefficient estimations (kL a). The study analyzed the effect of the impeller type, agitation speed, and power input on the tank's flow field and revealed that upward-pumping pitched blade impellers (PBI) in the top two positions (compared to Rushton-type) provided advantageous oil phase homogeneity and similar estimated kL a values with reduced power. These results show good agreement with the experimental mixing and kL a data.

Green Production of a High-value Mosquito Insecticide of Nootkatone from Seaweed Hydrolysates

Nootkatone is a type of valuable sesquiterpene that is widely used in food, cosmetics, fragrance, and other fields. The industry is faced with a major challenge due to the high expenses associated with plant-extracted nootkatone. We have developed a fermentation process for valencene production using seaweed hydrolysate as a carbon source via engineered Saccharomyces cerevisiae. Reduced-pressure distillation purified valencene was used as a substrate, and a yeast strain carrying HPO/AtCPR1 and ADH genes was constructed for whole-cell catalysis. After biotransformation at 25 °C for 3 h, a high yield of 73% for nootkatone production was obtained. Further, simple rotary evaporation was used to obtain nootkatone with a high purity of 97.4%. Mosquito-repellent testing showed that 1% nootkatone has a mosquito-repellent effect lasting up to 6 h, which is comparable to the 20% N,N-diethyl-meta-toluamide (DEET) effect. This study provided practical experience for developing third-generation biomass resources, generating new ideas for green manufacturing of valuable chemical products, and serving as a reference for creating efficient and eco-friendly mosquito repellents.

Isolation, purification, and mass spectrometry identification of the enzyme involved in citrus flavor (+)-valencene biotransformation to (+)-nootkatone by Yarrowia lipolytica

BACKGROUND

(+)-Nootkatone is a highly valuable sesquiterpene compound that can be used as an aromatic in the food industry because of its grapefruit flavor and low sensory threshold. The unconventional yeast Yarrowia lipolytica has many unique physical and chemical properties, metabolic characteristics, and genetic structure, which has aroused the interest of researchers. Previous research showed that Y. lipolytica possesses the ability to transform the sesquiterpene (+)-valencene to (+)-nootkatone. The aim of this study was to isolate, purify, and identify the enzyme involved in the (+)-valencene bioconversion to (+)-nootkatone by Y. lipolytica.

RESULTS

In this study, ultrasonic-assisted extraction, ammonium sulfate precipitation, anion-exchange chromatography, and gel-filtration chromatography were used to separate and purify the enzyme involved in the (+)-valencene bioconversion by Y. lipolytica. The protein was identified as aldehyde dehydrogenase (ALDH) (gene0658) using sodium dodecyl sulfate polyacrylamide gel electrophoresis and liquid chromatography-tandem mass spectrometry analysis. The ALDH had the highest activity when the pH value was 6.0 and the temperature was 30 °C. The activity of ALDH was significantly stimulated by ferrous ions and inhibited by barium, calcium, and magnesium ions.

CONCLUSION

This is the first time that ALDH was found to participate in (+)-valencene biotransformation by Y. lipolytica. It may be involved in regulating the microbial transformation of (+)-valencene to (+)-nootkatone through redox characteristics. This study provides a theoretical basis and reference for the biological synthesis of citrus flavor (+)-nootkatone. © 2023 Society of Chemical Industry.

A kinetic study of biotransformation from valencene to nootkatone in an oscillatory baffled reactor

In this paper we report our kinetic study of an oxidation reaction from valencene to nootkatone using enzyme in an oscillatory baffled reactor. The aims of this work are to elucidate the reaction mechanism and evaluate reaction kinetics. Towards these objectives, a full kinetic model using the Langmuir-Hinshelwood method was established and applied to the experimental data, allowing reactor schemes and orders to be confirmed and reaction rate constants to be extracted. Our full kinetic analysis suggests that most of the reversible reaction steps can be treated as irreversible, simplifying the overall reaction schemes. The effect of mass transfer on the kinetics was also investigated. © 2023 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

Differential proteomic analysis of citrus flavor (+)-valencene biotransformation to (+)-nootkatone by Yarrowia lipolytica

Natural products (+)-nootkatone is an important sesquiterpene compound and is widely used in pharmaceutical, cosmetic, agricultural and food industries. The aim of this study was to analyze the differentially expressed proteins (DEPs) during citrus aroma compound (+)-valencene biotransformation to (+)-nootkatone by Yarrowia lipolyticaby with high-throughput LC-MS/MS. A total of 778 proteins were differentially expressed, 385 DEPs were significantly up-regulated and 393 DEPs were markedly down-regulated. It was found that the enzymes transformed (+)-valencene to (+)-nootkatone were mainly existed in yeast intracellular and precipitated under the condition of 30-40 % ammonium sulfate. Most DEPs involved in amino acid and fatty acid metabolism were down-regulated during (+)-valencene biotransformation. The DEPs related to the carbohydrate metabolism, energy metabolism and most of transporter proteins were significantly up-regulated. Furthermore, the key enzymes involved in (+)-valencene transformation might be related to cytochrome P450s (gene2215 and gene2911) and dehydrogenases (gene6493). This is the first time that proteomics was used to investigate the metabolism mechanism of Yarrowia lipolytica during (+)-valencene biotransformation. The proteomic analysis of Yarrowia lipolytica provided a foundation for the molecular regulatory mechanism in the biotransformation to (+)-nootkatone from (+)-valencene.

Production of indole-3-acetic acid by Bacillus circulans E9 in a low-cost medium in a bioreactor

Bacillus circulans E9 (now known as Niallia circulans) promotes plant growth-producing indole-3-acetic acid (IAA), showing potential for use as a biofertilizer. In this work, the use of a low-cost medium containing industrial substrates, soybean, pea flour, Solulys, Pharmamedia, yeast extract, and sodium chloride (NaCl), was evaluated as a substitute for microbiological Luria Broth (LB) medium for the growth of B. circulans E9 and the production of IAA. In Erlenmeyer flasks with pea fluor medium (PYM), the maximum production of IAA was 7.81 ± 0.16 μg mL^-1, while in microbiological LB medium, it was 3.73 ± 0.15 μg mL^-1. In addition, an oxygen transfer rate (OTR) of 1.04 kg O₂ m^-3 d^-1 allowed the highest bacterial growth (19.3 ± 2.18 × 10¹⁰ CFU mL^-1) and IAA production (10.7 μg mL^-1). Consequently, the OTR value from the flask experiments was used to define the conditions for the operation of a 1 L stirred tank bioreactor. The growth and IAA production of B. circulans cultured in a bioreactor with PYM medium were higher (8 and 1.6 times, respectively) than those of bacteria cultured in Erlenmeyer flasks. IAA produced in a bioreactor by B. circulans was shown to induce the root system in Arabidopsis thaliana, similar to synthetic IAA. The results of this study demonstrate that PYM medium may be able to be used for the mass production of B. circulans E9 in bioreactors, increasing both bacterial growth and IAA production. This low-cost medium has the potential to be employed to grow other IAA-producing bacterial species.

Engineering Considerations to Produce Bioactive Compounds from Plant Cell Suspension Culture in Bioreactors

The large-scale production of plant-derived secondary metabolites (PDSM) in bioreactors to meet the increasing demand for bioactive compounds for the treatment and prevention of degenerative diseases is nowadays considered an engineering challenge due to the large number of operational factors that need to be considered during their design and scale-up. The plant cell suspension culture (CSC) has presented numerous benefits over other technologies, such as the conventional whole-plant extraction, not only for avoiding the overexploitation of plant species, but also for achieving better yields and having excellent scaling-up attributes. The selection of the bioreactor configuration depends on intrinsic cell culture properties and engineering considerations related to the effect of operating conditions on thermodynamics, kinetics, and transport phenomena, which together are essential for accomplishing the large-scale production of PDSM. To this end, this review, firstly, provides a comprehensive appraisement of PDSM, essentially those with demonstrated importance and utilization in pharmaceutical industries. Then, special attention is given to PDSM obtained out of CSC. Finally, engineering aspects related to the bioreactor configuration for CSC stating the effect of the operating conditions on kinetics and transport phenomena and, hence, on the cell viability and production of PDSM are presented accordingly. The engineering analysis of the reviewed bioreactor configurations for CSC will pave the way for future research focused on their scaling up, to produce high value-added PDSM.

Advances on (+)-nootkatone microbial biosynthesis and its related enzymes

(+)-Nootkatone is an important functional sesquiterpene and is comprehensively used in pharmaceutical, cosmetic, agricultural and food flavor industries. However, (+)-nootkatone is accumulated trace amounts in plants, and the demand for industry is mainly met by chemical methods which is harmful to the environment. The oxygen-containing sesquiterpenes prepared using microbial methods can be considered as "natural." Microbial transformation has the advantages of mild reaction conditions, high efficiency, environmental protection, and strong stereoselectivity, and has become an important method for the production of natural spices. The microbial biosynthesis of (+)-nootkatone from the main precursor (+)-valencene is summarized in this paper. Whole-cell systems of fungi, bacteria, microalgae, and plant cells have been employed. It was described that the enzymes involved in the microbial biosynthesis of (+)-nootkatone, including cytochrome p450 enzymes, laccase, lipoxygenase, and so on. More recently, the related enzymes were expressed in microbial hosts to heterologous produce (+)-nootkatone, such as Escherichia coli, Pichia pastoris, Yarrowia lipolytica, and Saccharomyces cerevisiae. Finally, the development direction of research for realizing industrialization of microbial transformation was summarized and it provided many options for future improved bioprocesses.

Effect of Biomass Concentration on Oxygen Mass Transfer, Power Consumption, Interfacial Tension and Hydrodynamics in a Multiphase Partitioning Bioreactor

Several studies have reported that the hydrodynamics are not affected by the biomass in multiphase partitioning bioreactors. This work aims to demonstrate the effect of biomass concentration (0, 1, 3 and 5 g L−1) on the oxygen mass transfer coefficients, the droplet size of the dispersed phase, power consumption and superficial tension in a multiphase partitioning bioreactor (ionic liquid-aqueous-air-biomass system). At a biomass concentration of 5 g L−1, the oxygen mass transfer coefficient (kLa) increased by 55% (249 h−1) compared with the abiotic system (160 h−1). In the multiphasic system, the droplet size (d32) decreased when the biomass concentration was increased, producing an increment in the mass transfer area of the dispersed phase. In addition, the power consumption decreased by 44 % compared to a previous report without biomass. Furthermore, the increment of biomass concentration decreased the superficial tension by up to 15 %. A biomass increment in a multiphase system not also increases product yield, but also enhances the bioconversion process. The results obtained suggest that it is obligatory to consider the effect of biomass concentration on hydrodynamic characterisation, design, scale-up and optimisation for improving the performance of biotechnological processes using multiphase bioreactors.