Biotransformation Processes Research Articles

Cyanobacteria-Mediated Light-Driven Biotransformation: The Current Status and Perspectives.

Most chemicals are manufactured by traditional chemical processes but at the expense of toxic catalyst use, high energy consumption, and waste generation. Biotransformation is a green, sustainable, and cost-effective process. As cyanobacteria can use light as the energy source to power the synthesis of NADPH and ATP, using cyanobacteria as the chassis organisms to design and develop light-driven biotransformation platforms for chemical synthesis has been gaining attention, since it can provide a theoretical and practical basis for the sustainable and green production of chemicals. Meanwhile, metabolic engineering and genome editing techniques have tremendous prospects for further engineering and optimizing chassis cells to achieve efficient light-driven systems for synthesizing various chemicals. Here, we display the potential of cyanobacteria as a promising light-driven biotransformation platform for the efficient synthesis of green chemicals and current achievements of light-driven biotransformation processes in wild-type or genetically modified cyanobacteria. Meanwhile, future perspectives of one-pot enzymatic cascade biotransformation from biobased materials in cyanobacteria have been proposed, which could provide additional research insights for green biotransformation and accelerate the advancement of biomanufacturing industries.

Physiology-informed toxicokinetic model for the zebrafish embryo test developed for bisphenols

Zebrafish embryos (ZFE) is a widely used model organism, employed in various research fields including toxicology to assess e.g., developmental toxicity and endocrine disruption. Variation in effects between chemicals are difficult to compare using nominal dose as toxicokinetic properties may vary. Toxicokinetic (TK) modeling is a means to estimate internal exposure concentration or dose at target and to enable extrapolation between experimental conditions and species, thereby improving hazard assessment of potential pollutants. In this study we advance currently existing TK models for ZFE with physiological ZFE parameters and novel experimental bisphenol data, a class of chemicals with suspected endocrine activity. We developed a five-compartment model consisting of water, plastic, chorion, yolk sack and embryo in which surface area and volume changes as well as the processes of biotransformation and blood circulation influence mass fluxes. For model training and validation, we measured internal concentrations in ZFE exposed individually to BPA, bisphenol AF (BPAF) and Z (BPZ). Bayesian inference was applied for parameter calibration based on the training data set of BPZ. The calibrated TK model predicted internal ZFE concentrations of the majority of external test data within a 5-fold error and half of the data within a 2-fold error for bisphenols A, AF, F, and tetrabromo bisphenol A (TBBPA). We used the developed model to rank the hazard of seven bisphenols based on predicted internal concentrations and measured in vitro estrogenicity. This ranking indicated a higher hazard for BPAF, BPZ, bisphenol B and C (BPB, BPC) than for BPA.

Oxidative stress in animals exposed to cypermethrin: mechanisms of development and possible risks

The purpose of the study is to establish the mechanisms of development of oxidative stress during long-term low-dose exposure to cypermethrin on the animal organism and to substantiate possible risks. The work was carried out using Wistar rats, which were intragastrically injected daily with cypermethrin at a dose of 1/1000 LD50 for 60 and 120 days. At the same time, control animals received an appropriate volume of saline solution inside. When removing animals from the experiment, blood was taken to determine the number of red blood cells, the concentration of hemoglobin, glucose, lactic and uric acids, and total bilirubin. In the study of erythrocytes and liver, biochemical parameters characterizing carbohydrate and purine metabolism, processes of xenobiotics biotransformation, pro- and antioxidant processes were determined. Long-term lowdose exposure to cypermethrin for 60 days causes hematotoxic effects in animals, enhancement of xenobiotic biotransformation processes, and slight compensatory restructuring of metabolic processes in the liver. Exposure to 1/1000 LD50 of cypermethrin for 120 days, in addition to the above effects, causes the development of acidosis, enhances pro-oxidant processes, and suppresses the function of the antioxidant defense system and the pentose cycle. The decrease in the activity of the liver antioxidant system is due to glutathione deficiency due to the activation of xenobiotic biotransformation systems and suppression of the activity of glutathione reductase and glucose-6- phosphate dehydrogenase, which ultimately leads to the development of oxidative stress. Long-term exposure of animals to low doses of cypermethrin causes hemolysis of erythrocytes, lactic acidosis, activation of prooxidant systems, and inhibition of the antioxidant defense system. Deficiency of carbohydrates and suppression of the activity of the pentose cycle indicate a decrease in the functional activity of the liver and an increased risk of immunosuppression.

Antifungal activity of clove basil (Ocimum gratissimum L.) beverage fermented with kombucha culture

Fungi are associated with several diseases in humans, however these diseases have been neglected over the years. Fungal infections are estimated to cause more than 1.5 million deaths annually. In addition, recent studies have revealed the presence of pathogens resistant to antifungal drugs available for treatment. In view of this scenario, it is necessary to invest in research aimed at the discovery and development of new antifungal therapies. An important aspect to be considered is the antimicrobial activity attributed to fermented beverages, such as kombucha, which is obtained from the fermentation of an infusion of plant parts by a symbiotic consortium of bacteria and yeast known as SCOBY (Symbiotic Culture of Bacteria and Yeast). In this context, the aim of this work was to elaborate a fermented beverage based on clove basil (Ocimum gratissimum L.) (CBK) and to evaluate its antimicrobial activity against fungi Candida albicans, Candida auris, Candida glabrata, Candida tropicalis and Cryptococcus neoformans. CBK has presented pH values within the required legislation for kombucha, demonstrating quality and safety standards in the fermentation process. As for antimicrobial analysis, CBK fermented for 15 days showed antifungal effect on all tested strains, however, the fungicidal effect was only verified against C. albicans, C. auris e C. neoformans. Thus, this study contributes to the description of a new source of antifungal substances and opens perspectives for future research on the biotransformation processes of chemical compounds during fermentation procedures.

Utilisation of Insect Gut as a Biosource for the Development of Future Biotransformation Processes

Sustainability has been one of the main issues in the world in recent years. The decrease of resources in the world, along with the growing world population and the resulting environmental waste, present a fairly significant problem. As an alternative solution to this problem, insects are put forward as an ideal resource. Due to the enzymes and microorganisms in their intestinal microbiota, the biotransformation processes of insects are capable of converting wastes, organic materials and residues into valuable products that can be used for various industrial applications such as pharmaceuticals, cosmetics and functional foods. Some species of insects are in an advantageous position because of the simplicity of their lifecycle, the ease of their production and their ability to feed on organic materials to make valuable products. From a sustainability perspective, utilisation of the microorganisms or enzymes isolated from these microorganisms available in the microbiota of insects may allow novel insect-based biotransformation processes that promise a more sustainable world and novel green technologies.

Bioconversion performances of black soldier fly larvae (<em>Hermetia illucens</em> L. Diptera: Stratiomyidae) on selected organic substrates

Black Soldier Fly Larvae (BSFL; Hermetia illucens L.) is a bioconversion agent of organic substrates and its proven ability to degrade and biotransform of waste strengthens organic waste management and waste recycling strategies. BSFL have the advantages of rapid development and very efficient conversion of various organic wastes into body biomass. This process reduces the disposal costs of organic waste as well as the use of energy providing a sustainable solution to the treatment of organic waste. In addition, it provides valuable products and fertilizers for agriculture, potentially reducing crop production costs for farmers. The current study investigated the potential live biomass production of BSFL using different organic substrates available locally while understanding their decomposition ability. Seven treatments were compared (T1- equal proportion of poultry manure and rice bran, T2- equal proportion of goat manure and rice bran, T3- rabbit droppings, T4- soybean meal, T5- coconut scrapings, T6- equal proportion of vegetable and fruit waste and T7- cow dung) and the experiment was set up as completely randomized design with three replicates. The study results examined the ability of BSFL to reduce the weight of the end-substrate and promote the degradation of organic waste materials. The live biomass production of larvae, changes in live biomass production, substrate consumption rate, the weight of the end-substrate and substrate conversion efficiency were significantly different among treatments. The greatest live biomass production of BSFL was recorded in coconut scrapings and vegetables & fruit waste mixture while the lowest value was observed in cow dung. Coconut scrapings reduced most of their weight at the end of the study indicating the highest substrate consumption rate and the total weight of the end-substrate consisted of < 2mm particle in size. However, the highest substrate conversion rate was observed in cow dung. Aqueous solutions prepared from the end-substrates varied widely in pH, electrical conductivity, total dissolved solids, and salinity. In addition, significant differences were found among treatments for the colour and texture of the end-substrate. However, the appearance and odour did not differ significantly. According to the results of the present study, it can be concluded that the most efficient media for BSFL was coconut scraping though; it cannot be used as organic fertilizer as it exceeded the pH value of the SLS recommendation for compost. Overall, BSFL can be recognized as an effective and environmentally friendly tool to use in the biotransformation process of locally available organic waste materials.

Bioaccessibility Evaluation of Soymilk Isoflavones with Biotransformation Processing.

Soy isoflavones are considered important sources of bioactive compounds, but they are poorly absorbable, due to their large hydrophilic structures. Some biotransformation strategies have been used to convert the glycosidic form into aglycones, making them available for absorption. This study evaluated the potential of enzymatic and/or microbial fermentation combined bioprocesses in a soymilk extract before and after gastrointestinal in vitro digestion. Commercial β-glucosidase (ET) and a mix of commercial probiotics (F) containing Lactobacillus acidophilus, Lactobacillus casei, Lactococcus lactis, Bifidobacterium bifidum, and Bifidobacterium lactis were used to biotransform the soymilk phenolic extract. An isoflavone profile was identified using HPLC-DAD, total phenolic content was identified using the Folin-Ciocalteu test, and antioxidant capacity was identified using ORAC and FRAP. Soymilk enzymatically treated (ET) followed by microbial fermentation (ET + T) resulted in better conversion of glycosylated isoflavones (6-fold lower than control for daidzin and 2-fold for genistin) to aglycones (18-fold greater than control for dadzein and genistein). The total phenolic content was increased (3.48 mg/mL for control and 4.48 mg/mL for ET + T) and the antioxidant capacity was improved with treatments of ET + T (120 mg/mL for control and 151 mg/mL with ORAC) and with FRAP (285 µL/mL for control and 317 µL/mL). After the in vitro digestion, ET + T samples resulted in a higher content of genistein (two-fold higher than control); also, increases in the total phenolic content (2.81 mg/mL for control and 4.03 mg/mL for ET + T) and antioxidant capacity measured with ORAC were greater compared to undigested samples. In addition, the isolated microbial fermentation process also resulted in positive effects, but the combination of both treatments presented a synergistic effect on soy-based products.

Production of perillic acid from orange essential oil by Yarrowia lipolytica using a top-aerated bioreactor.

R-(+)-Perillic acid, a promising anticancer and immunomodulatory agent, is the major product from the biotransformation of R-(+)-limonene-rich orange essential oil by the yeast Yarrowia lipolytica. Due to the abundance and low cost of orange essential oil, which is a byproduct of the citrus industry, we attempted to improve the biotransformation process by optimizing yeast cell mass production. Then, the whole process was transposed and adapted to a 2-L instrumented bioreactor. Cell mass production was optimized in shaker flasks using a statistical experimental design. The optimized medium (g·L-1: 22.9 glucose, 7.7 peptone, 4.1 yeast extract and 1.0 malt extract) resulted in a 13.0g·L-1 final cell concentration and 0.18g cell·L-1·h-1 productivity. A further increase to 18.0g·L-1 was achieved in a 2-L bioreactor upon fed-batch culture. High-purity limonene bioconversion was performed in the same bioreactor utilizing top aeration to diminish terpene volatilization; as a result, 839.6mg·L-1 perillic acid accumulated after 48h. Under the same conditions, industrial orange essential oil afforded 806.4mg·L-1 perillic acid. The yeast growthmedium optimization resulted in a twofold increase in biomass accumulation and a reduction in growth medium nitrogen sources, which lowered the catalytic biomass production cost. Compared with conventional bottom aeration, the bioreactor top aeration strategy resulted in higher bioconversion rates. The conditions developed for high-purity limonene bioconversion were successfully applied to low-cost orange essential oil, showing the robustness ofY. lipolyticayeast.

ANALYSIS OF INDIGENOUS BACTERIAL FLORA FOUND IN LEAD CONTAMINATED SOIL OF FAISALABAD AND HARVESTING ITS ABILITY FOR BIOREMEDIATION

Some microorganisms have the ability to either degrade or remove environmental pollutants and could serve an effective role in bioremediation. Lead is a chemically inert heavy metal and if present in toxic amount in environment, can have negative health effects by becoming a part of the natural food chain. The main objective of this experiment was to identify soil micrbiota present in Pb contaminated soil of Faisalabad. WHO has reported elevated levels of lead contamination in water, and air across major cities in Pakistan. It majorly affects children aged 3-5 years and the urban population residing in major cities in Pakistan. Major source of Pb exposure in Pakistan are industrial wastes and effluents discharged directly into environment and it has toxic effects on the human nervous, renal and reproductive systems. Molecular Docking via CB dock is performed taking some bacterial proteins as receptors molecules and lead salts as ligand molecule for insilico analysis of bacterial strain involved in biosorption or biotransformation process. To identify lead tolerant bacteria, soil samples were collected from Pb contaminated sites near Faisalabad, followed by inoculation and purification of bacterial colonies in lead nitrate based culture media. UV spectrophotometry was performed and the colony showing maximum growth rate was subjected to 16s rRNA and Phylogenetic analyses. The identified bacterial species possesses considerably high lead tolerance and further analyzed for potential lead biosorption capabilities.

Intensification of biocatalytic processes by using alternative reaction media

Abstract Performances of biocatalytic processes in industry are often limited by productivity, product concentration and biocatalyst stability. Reasons can be such as unfavourable reaction thermodynamics, low water solubility of the substrates or inhibition caused by high substrate or product concentrations. A way to overcome these limitations and to enhance economic competitiveness of the process can be process intensification (PI) using an alternative reaction medium. Very early in industrial biotransformation processes, it was shown that many interesting target products of organic synthesis are much more soluble and sometimes even more stable in non-conventional reaction media than in buffered aqueous solutions. Moreover, the absence of water is also generally desired to prevent side and degradation reactions as well as microbial contamination, which in turn eliminates the need to work under sterile conditions thereby reducing energy expenditure. In addition, it was also discovered early on that solvents can influence the activity and stability of enzymes quite differently depending on their water affinity and thus if they form rather monophasic or biphasic systems with the latter.

Analysis of null deletion polymorphism of glutathione S-transferase theta (GSTT-1), associated with anti-GSTT-1 antibodies development in transplantation.

Glutathione S-transferase theta 1 (GSTT1) is an enzyme involved in phase II biotransformation processes and a member of a multigene family of detoxifying and clearing reactive oxygen species. GSTT1 is polymorphic like other biotransforming enzymes, allowing variability in hepatic conjugation processes. Immunological recognition of the GSTT1 alloantigen, as evidenced by donor-specific antibodies formation, has previously been observed in recipients lacking GSTT1 protein (called GSTT1-, GSTT*0, null phenotype or homozygous for the GSTT1 deletion) who receive liver or kidney transplants from GSTT1+ donors and is a risk factor for the development of de novo hepatitis following liver transplants from a GSTT1 expressing donor. Antibodies against GSTT1 are demonstrated in patients who are GSTT1 null and received a transplant from a GSTT1+ donor. Understanding the local population frequency of the GSTT1 deletion is of value in understanding the potential clinical risk of developing post-transplant complications, which can be attributed to the nonexpression of GSTT1. A population of 173 healthy donors of the Murcia Region in Southeast Spain was evaluated for a null allele of GSTT1 (n=173). DNA was extracted, and GSTT-1 null allele detection was performed by real-time polymerase chain reaction. The frequency of the null GSTT1 genotype (nonexpression or deletion of the homozygous polymorphism of the GSTT1 protein) was 17.9% (n=31 null allele GSTT1/173 total individuals). Our data suggest that the frequency of null GSTT1 mutations in our population in Southeast Spain is 17.9%, lower than in other Caucasoid populations. This would convert our recipient population into more susceptible to nonlocal potential organ donors and less susceptible to local donors. All recipients bearing this GSTT1 deletion homozygous would be without the protein and triggering an alloantigen in the case of transplantation with a donor without deletion.

The Use of Tail as a Minimal-Invasive Method to Detect a Large Set of Biochemical Responses in the Italian Wall Lizard Podarcis siculus (Rafinesque, 1810)

Conventional methods to analyze biochemical processes related to contaminant toxicity usually require the sacrifice of animals to collect tissues and organs. However, for ethical reasons and especially for endangered species, non- or minimal-invasive methods should be preferred. Among vertebrates, reptiles show a general decline worldwide and therefore the use of non- or minimal-invasive methods to measure some biochemical processes in these animals are encouraged. It is well known that most lizards use a common safety behavior implying the natural loss of tail in the case of predation events. Therefore, if common analyses testing contaminant toxicity could be performed in tail tissue, this method, not implying the sacrifice of the animals, could be considered as a good minimal-invasive method. The aim of this study is to test on wild Italian wall lizard Podarcis siculus the use of tail to detect a large set of biomarkers including oxidative stress (TOSCAROO, TOSCAOH, CAT, tGSH, MDA), biotransformation processes (EROD, GSTs) and neurotoxicity (AChE, BChE). All the biochemical responses, excluding EROD and MDA, resulted to be analytically detectable in tail tissues of P. siculus, although the mean values obtained with this minimal-invasive method were significantly lower than those obtained with invasive one.

Multi-omics analysis unravels effects of salt and oil on substance transformation, microbial community, and transcriptional activity in food waste anaerobic digestion

In this study, through quantitative detection of key substances and enzyme activities, an integrated analysis of 16S rRNA sequencing and metatranscriptomics revealed the mechanisms by which salt and oil influence the biotransformation process during anaerobic digestion (AD). The results demonstrated that a salt concentration of 6 g/L promoted lipid metabolism and hydrogenotrophic methanogenesis, while inhibiting the acetoclastic pathway. An oil concentration of 5 g/L facilitated the expression of key enzyme-encoding genes involved in β-oxidation of long-chain fatty acids, transcription, and acetoclastic methanogenesis. It also promoted the enrichment of syntrophic propionate/butyrate oxidation bacteria (Syntrophomonas and DMER64). Salt/oil co-addition enhanced the expression of genes related to glucose metabolism, amino acid metabolism, organic acid synthesis, and quorum sensing. Furthermore, salt/oil co-addition inhibited the secretion of key enzymes related to methanogens by impeding the transcription process. Collectively, these findings provide systematic insights into how salt and oil affect the biochemical metabolic mechanisms of AD.

Enantioselective uptake, translocation, and biotransformation of pydiflumetofen in wheat (Triticum aestivum L.): Insights from chiral profiling and molecular simulation

Pydiflumetofen (PYD), a highly effective and broad-spectrum fungicide, is commonly employed for the control of fungal diseases. In this study, the uptake, translocation, and biotransformation of PYD by wheat (Triticum aestivum L.) were firstly investigated at a chiral level. The findings revealed that the residue concentration of R-PYD in wheat was higher than that of S-PYD, because of its higher uptake rate (k1 = 0.0421 h−1) and lower elimination rate (k2 = 0.0459 h−1). Additionally, R-PYD exhibited higher root bioconcentration factors and translocation factors compared with S-enantiomer, indicating R-PYD was more easily accumulating in roots and translocating to shoots. Furthermore, a total of 9 metabolites, including hydroxylated, demethylated, demethoxylated, dechlorinated, hydrolyzed, and glycosylated-conjugated products, were detected qualitatively in wheat roots or shoots. Symplastic pathway-mediated uptake, which predominantly relied on aquaporins and anion channels, was confirmed by root adsorption and inhibition experiments, without displaying any enantioselective effect. Molecular simulations demonstrated that R-PYD exhibited stronger binding affinity with TaLTP 1.1 with a lower grid score (−6.79 kcal/mol), whereas weaker interaction with the metabolic enzyme (CYP71C6v1) compared to the S-enantiomer. These findings highlight the significance of plant biomacromolecules in the enantioselective bioaccumulation and biotransformation processes. Importantly, a combination of experimental and theoretical evidence provide a comprehensive understanding of the fate of chiral pesticides in plants from an enantioselective perspective.

Biotransformation of Microcrystalline Cellulose from Rice Straw Waste using TGJPC-120 Bacteria and its Characterization

Microcrystalline Cellulose, MCC, is widely used in pharmaceutical, cosmetics, food, and other industries. This study aims to see changes in the properties that occur in MCC from rice straw waste after transformation using TGJPC-120 isolated bacteria from soil. The biotransformation process was carried out in the bacterial culture flask and placed in an incubator shaker for 2 days at 37 °C, at a rate of 100 rpm. The surface morphology of MCC obtained before and after biotransformation was observed by Scanning Electron Microscopy (SEM). The IR-spectrum and Evaluation of Solid State Interaction of MCC were tested by Fourier Transformation Infra Red (FTIR) Spectrophotometer and Differential Scanning Calorimetry (DSC), respectively. Crystalline characteristics of MCC were analyzed by X-Ray Diffraction technique, and identification of TGJPC-120 was carried out by 16S rRNA analysis. The results showed that DSC thermogram of unbiotransformed and biotransformed-MCC showed the changing in peak width from wide to sharper peaks, reduction in the intensity, and shifts in the melting point. Physical interaction occurs during the biotransformation process to produce a new crystalline phase, and there is no chemical interaction between components during the biotransformation process. The relationship between TGJPC-120 bacteria and Pseudomonas rhizosphaerae Strain IH5 was 92% in the BLAST program tracking database which was determined based on the phylogenetic tree. It can be concluded that the characteristics of MCC before and after the transformation process are different. Studies for process optimization are still ongoing at this time.

Aroma Profile Development in Beer Fermented with Azacca, Idaho-7, and Sultana Hops.

Hops are among the most costly and environmentally impactful raw materials used in brewing, yet they play a crucial role in the aroma of beer. However, predicting beer aroma based on hop variety or hopping method remains arduous. This is partly because hop oils are unique for each hop variety, and they may be biotransformed by yeast enzymes during fermentation. Even slight molecular structure modifications can dramatically affect the organoleptic properties of beer. Through combined chemical and sensory analysis of dry-hopped beers prepared with different hop varieties (Azacca, Idaho-7, and Sultana), this work aimed to profile the aromas and the overall biotransformation processes taking place during fermentation. A total of 51 volatile organic compounds (VOCs) were semi-quantified and monitored: 19 esters, 13 sesquiterpenes, 7 ketones, 7 alcohols, 4 monoterpenes, and 1 volatile acid. There were significant similarities in the measured analytes and perceived aromas of these beers, but one hop variety (Sultana) delivered an increased quantity of unique aromas and an increased concentration of volatiles in the headspace for the same quantity of hop pellets added. This work provides practical information to brewers who utilize hops in beer production.

Glycosylation of Quercetin by Selected Entomopathogenic Filamentous Fungi and Prediction of Its Products' Bioactivity.

Quercetin is the most abundant flavonoid in food products, including berries, apples, cauliflower, tea, cabbage, nuts, onions, red wine and fruit juices. It exhibits various biological activities and is used for medical applications, such as treating allergic, inflammatory and metabolic disorders, ophthalmic and cardiovascular diseases, and arthritis. However, its low water solubility may limit quercetin's therapeutic potential. One method of increasing the solubility of active compounds is their coupling to polar molecules, such as sugars. The attachment of a glucose unit impacts the stability and solubility of flavonoids and often determines their bioavailability and bioactivity. Entomopathogenic fungi are biocatalysts well known for their ability to attach glucose and its 4-O-methyl derivative to bioactive compounds, including flavonoids. We investigated the ability of cultures of entomopathogenic fungi belonging to Beauveria, Isaria, Metapochonia, Lecanicillium and Metarhizium genera to biotransform quercetin. Three major glycosylation products were detected: (1), 7-O-β-D-(4″-O-methylglucopyranosyl)-quercetin, (2) 3-O-β-D-(4″-O-methylglucopyranosyl)-quercetin and (3) 3-O-β-D-(glucopyranosyl)-quercetin. The results show evident variability of the biotransformation process, both between strains of the tested biocatalysts from different species and between strains of the same species. Pharmacokinetic and pharmacodynamic properties of the obtained compounds were predicted with the use of cheminformatics tools. The study showed that the obtained compounds may have applications as effective modulators of intestinal flora and may be stronger hepato-, cardio- and vasoprotectants and free radical scavengers than quercetin.

Bioconversion of vitamin D3 into calcitriol by Actinomyces hyovaginalis isolate CCASU- A11-2

Vitamin D3 is a fat-soluble prohormone that is activated inside the liver to produce 25-hydroxyvitamin D3 (calcidiol), and in the kidney to produce the fully active 1α, 25-dihydroxy vitamin D3 (calcitriol). A previous work piloted in our laboratory, resulted in a successful recovery of a local soil-promising Actinomyces hyovaginalis isolate CCASU-A11-2 capable of converting vitamin D3 into calcitriol. Despite the rising amount of research on vitamin D3 bioconversion into calcitriol, further deliberate studies on this topic can significantly contribute to the improvement of such a bioconversion process. Therefore, this work aimed to improve the bioconversion process, using the study isolate, in a 14 L laboratory fermenter (4 L fermentation medium composed of fructose (15 g/L), defatted soybean (15 g/L), NaCl (5 g/L), CaCO3 2 g/L); K2HPO4, (1 g/L) NaF (0.5 g/L) and initial of pH 7.8) where different experiments were undertaken to investigate the effect of different culture conditions on the bioconversion process. Using the 14 L laboratory fermenter, the calcitriol production was increased by about 2.5-fold (32.8 µg/100 mL) to that obtained in the shake flask (12.4 µg/100 mL). The optimal bioconversion conditions were inoculum size of 2% v/v, agitation rate of 200 rpm, aeration rate of 1 vvm, initial pH of 7.8 (uncontrolled); addition of vitamin D3 (substrate) 48 h after the start of the main culture. In conclusion, the bioconversion of vitamin D3 into calcitriol in a laboratory fermenter showed a 2.5-fold increase as compared to the shake flask level where, the important factors influencing the bioconversion process were the aeration rate, inoculum size, the timing of substrate addition, and the fixed pH of the fermentation medium. So, those factors should be critically considered for the scaling-up of the biotransformation process.

Bidirectional Interactions between Green Tea (GT) Polyphenols and Human Gut Bacteria.

Green tea (GT) polyphenols undergo extensive metabolism within gastrointestinal tract (GIT), where their derivatives compounds potentially modulate the gut microbiome. This biotransformation process involves a cascade of exclusive gut microbial enzymes which chemically modify the GT polyphenols influencing both their bioactivity and bioavailability in host. Herein, we examined the in vitro interactions between 37 different human gut microbiota and the GT polyphenols. UHPLC-LTQ-Orbitrap-MS/MS analysis of the culture broth extracts unravel that genera Adlercreutzia, Eggerthella and Lactiplantibacillus plantarum KACC11451 promoted C-ring opening reaction in GT catechins. In addition, L. plantarum also hydrolyzed catechin galloyl esters to produce gallic acid and pyrogallol, and also converted flavonoid glycosides to their aglycone derivatives. Biotransformation of GT polyphenols into derivative compounds enhanced their antioxidant bioactivities in culture broth extracts. Considering the effects of GT polyphenols on specific growth rates of gut bacteria, we noted that GT polyphenols and their derivate compounds inhibited most species in phylum Actinobacteria, Bacteroides, and Firmicutes except genus Lactobacillus. The present study delineates the likely mechanisms involved in the metabolism and bioavailability of GT polyphenols upon exposure to gut microbiota. Further, widening this workflow to understand the metabolism of various other dietary polyphenols can unravel their biotransformation mechanisms and associated functions in human GIT.

Multiple isotopes reveal the driving forces of nitrogen cycling from freshwater to brackish water

Rivers play a crucial role in global nitrogen (N) cycling, but revealing the driving mechanism of N cycling remains challenging because of the complex natural background gradients. The Qiantang River Basin provides an opportunity to elucidate the driving mechanism due to the complex climatic and hydrological conditions. In this study, the multiple stable isotopes suggested that the conservative mixing of two end members was insufficient to explain the complex behavior of N in both seasons. In-soil processes were the primary N cycling processes that controlled riverine N loading during the wet season, whereas in-stream N biological transformation processes (nitrification and assimilation) were more prevalent during the dry season. The results of MixSIAR revealed that soil sources (soil N and N fertilizer) contributed the most to NO3− during the wet season, accounting for 64.3 %, followed by manure and sewage (31.6 %) and atmospheric precipitation (4.1 %). During the dry season, manure and sewage were the predominant contributors to NO3− (52.1 %), followed by soil N (26.6 %), N fertilizer (18.8 %), and atmospheric precipitation (2.5 %). The relationships between d-excess and δ15N-NH4+ or δ15N-NO3− suggested that both climatic and hydrological conditions would be the driving forces regulating the N transportation and transformation in this basin, leading to the high spatiotemporal heterogeneity in N loading and isotopic compositions. In the wet season, precipitation patterns served as the primary driving forces regulating in-soil biological processes and soil leaching. While the hydrological conditions, especially water residence time, were the crucial factors controlling in-stream biological processes during the dry season. This study elucidates N sources, biotransformation processes, and their driving forces from freshwater to brackish water, which has applications for understanding the N fate from terrene to ocean.