Microbial Biotransformation Research Articles

Microbial and enzymatic strategies for the production of L-ribose.

L-Ribose is a non-naturally occurring pentose that recently has become known for its potential application in the pharmaceutical industry, as it is an ideal starting material for use in synthesizing L-nucleosides analogues, an important class of antiviral drugs. In the past few decades, the synthesis of L-ribose has been mainly undertaken through the chemical route. However, chemical synthesis of L-ribose is difficult to achieve on an industrial scale. Therefore, the biotechnological production of L-ribose has gained considerable attention, as it exhibits many merits over the chemical approaches. The present review focuses on various biotechnological strategies for the production of L-ribose through microbial biotransformation and enzymatic catalysis, and in particular on an analysis and comparison of the synthetic methods and different enzymes. The physiological functions and applications of L-ribose are also elucidated. In addition, different sugar isomerases involved in the production of L-ribose from a number of sources are discussed in detail with regard to their biochemical properties. Furthermore, analysis of the separation issues of L-ribose from the reaction solution and different purification methods is presented.Key points • l -Arabinose, l -ribulose and ribitol can be used to produce l -ribose by enzymes. • Five enzymes are systematically introduced for production of l -ribose. • Microbial transformation and enzymatic methods are promising for yielding l -ribose.

Chloroanisoles and Chlorophenols Explain Mold Odor but Their Impact on the Swedish Population Is Attributed to Dampness and Mold.

We recently reported that mold odor may be explained by chloroanisoles (CAs) formed by microbial biotransformation of chlorophenols (CPs) in legacy wood preservatives. Here we examine psychophysical aspects of CAs and trace their historic origins in buildings. Our exposure of healthy volunteers shows that 2,4,6-triCA is often perceived as unpleasant, characterized as musty or moldy and is detected at 13 ng/m3 or lower. Similar concentrations are reported in buildings with odor complaints. Scrutiny of written records reveal that new building construction methods were introduced in the 1950s, namely crawlspaces and concrete slabs on the ground. These constructions were prone to dampness and attack from wood decay fungi, prompting chemical companies and authorities to advocate preservatives against rot. Simultaneously, CPs became household chemicals used for example in indoor paints. When large-scale odor problems evolved, the authorities that once approved the preservatives attributed the odor to hidden mold, with no evidence that substantial microbial biomass was necessary for odor formation. Thereby the public remained unaware of problematic exposure to CPs and CAs. We conclude that the introduction of inappropriate designs of house foundations and CP-based preservatives once ignited and still provide impetus for indoor air research on “dampness and mold”.

Biotransformation strategies for steroid estrogen and androgen pollution.

The common steroid hormones are estrone (E1), 17β-estradiol (E2), estriol (E3), 17α-ethinylestradiol (EE2), and testosterone (T). These steroids are reported to contaminate the environment through wastewater treatment plants. Steroid estrogens are widespread in the aquatic environment and therefore pose a potential risk, as exposure to these compounds has adverse impacts on vertebrates. Excessive exposure to steroid estrogens causes endocrine disruption in aquatic vertebrates, which affects the normal sexual life of these animals. Steroid pollutants also cause several health problems in humans and other animals. Microbial degradation is an efficient method for removing hormone pollutants from the environment by remediation. Over the last two decades, microbial metabolism of steroids has gained considerable attention due to its higher efficiency to reduce pollutants from the environment. The present review is focused on the major causes of steroid pollution, concentrations of these pollutants in surface water, groundwater, drinking water, and wastewater, their effect on humans and aquatic animals, as well as recent efforts by various research groups that seek better ways to degrade steroids by aerobic and anaerobic microbial systems. Detailed overview of aerobic and anaerobic microbial biotransformation of steroid estrogens and testosterone present in the environment along with the active enzyme systems involved in these biotransformation reactions is described in the review article, which helps readers to understand the biotransformation mechanism of steroids in depth. Other measures such as co-metabolic degradation, consortia degradation, algal, and fungal steroid biotransformation are also discussed in detail.

Biotransformation of benzaldehyde into L-phenylacetylcarbinol using magnetic nanoparticles-coated yeast cells.

The yeast cells were coated with Fe3O4 magnetic nanoparticles and employed as biocatalyst for the microbial biotransformation of benzaldehyde into L-phenylacetylcarbinol (L-PAC). Saccharomyces cerevisiae CEN.PK113-7D yeast cells were coated with magnetic nanoparticles to facilitate the cells separation process. Transmission electron microscopy, powder XRD diffraction, and vibrating sample magnetometer were used to characterize magnetic nanoparticles and magnetic nanoparticle-coated yeast cells. Then the reusability of magnetically recoverable cells in production of L-PAC was investigated. Results show that coating yeast cells with magnetic nanoparticles does not affect their size and structure. Coated cells were also used in seven consecutive batch cycles and no significant reduction for L-PAC titer was observed in any of the cycles. Coating yeast cells with magnetic nanoparticles enabled rapid separation and reuse of cells in several successive batch cycle without affecting their ability to produce L-PAC.

The role of human and microbial metabolites of triptophane in severe diseases and critical ill (review)

The growing interest in metabolite circulating in the blood is associated with the accumulation of factual material on the involvement of low-molecular compounds in the development of a number of serious diseases. This review reveals the effect of a whole class of chemical compounds― tryptophan metabolites― on various pathological processes. The following keywords were used to find papers published in the PubMed database for the last 10 years: names of natural indole compounds, methods for their detection, nosology of diseases and critical ill patients. The data is presented in sections, which provide data on the study of tryptophan metabolites in a variety of groups of diseases, such as cancer, cardiovascular disease, kidney disease, bowel, mental disorders, atherosclerosis, etc. Particular attention is paid to the role of indole compounds that enter the systemic circulation as a result of microbial biotransformation of tryptophan, serotonin and other indole metabolites, which can be attributed to the "common metabolites" of humans and microbiota. The most interesting clinical studies are summarized in summary tables and figures. A number of indole metabolites are considered as potential biomarkers. The authors of the review substantiate the metabolomic approach to the study of a number of oncological, septic, mental and other intractable diseases, which opens up new possibilities of influence on the pathological process by targeted regulation in the metabolome/microbiome system.

P10 - Use of microbial biotransformation to produce scalable quantities of a glucuronidated metabolite of the clinical-stage soluble guanylate cyclase inhibitor praliciguat

P10 - Use of microbial biotransformation to produce scalable quantities of a glucuronidated metabolite of the clinical-stage soluble guanylate cyclase inhibitor praliciguat

The Effect of Hops (Humulus lupulus L.) Extract Supplementation on Weight Gain, Adiposity and Intestinal Function in Ovariectomized Mice.

Estrogen decline during menopause is associated with altered metabolism, weight gain and increased risk of cardiometabolic diseases. The gut microbiota also plays a role in the development of cardiometabolic dysfunction and is also subject to changes associated with age-related hormone changes. Phytoestrogens are plant-based estrogen mimics that have gained popularity as dietary supplements for the treatment or prevention of menopause-related symptoms. These compounds have the potential to both modulate and be metabolized by the gut microbiota. Hops (Humulus lupulus L.) contain potent phytoestrogen precursors, which rely on microbial biotransformation in the gut to estrogenic forms. We supplemented ovariectomized (OVX) or sham-operated (SHAM) C57BL/6 mice, with oral estradiol (E2), a flavonoid-rich extract from hops, or a placebo carrier oil, to observe effects on adiposity, inflammation, and gut bacteria composition. Hops extract (HE) and E2 protected against increased visceral adiposity and liver triglyceride accumulation in OVX animals. Surprisingly, we found no evidence of OVX having a significant impact on the overall gut bacterial community structure. We did find differences in the abundance of Akkermansia muciniphila, which was lower with HE treatment in the SHAM group relative to OVX E2 treatment and to placebo in the SHAM group.

Colonic Bacteria-Transformed Catechin Metabolite Response to Cytokine Production by Human Peripheral Blood Mononuclear Cells.

Human gut microbes are a profitable tool for the modification of food compounds into biologically active metabolites. The biological properties of catechins have been extensively investigated. However, the bioavailability of catechin in human blood plasma is very low. This study aimed to determine the biotransformed catechin metabolites and their bioactive potentials for modulating the immune response of human peripheral blood mononuclear cells (PBMCs). Biotransformation of catechin was carried out using in-vitro gut microbial biotransformation method, the transformed metabolites were identified and confirmed by gas chromatography-mass spectrometry (GC–MS) and high-performance liquid chromatography-mass spectrometry (HPLC–MS). Present observations confirmed that the catechin was biotransformed into 11 metabolites upon microbial dehydroxylation and C ring cleavage. Further, immunomodulatory potential of catechin metabolites was analyzed in peripheral blood mononuclear cells (PBMCs). We found up-regulation of anti-inflammatory cytokine (IL-4, IL-10) and down-regulation of pro-inflammatory (IL-16, IL-12B) cytokine may be due to Th2 immune response. In conclusion, biotransformed catechin metabolites enhance anti-inflammatory cytokines which is beneficial for overcoming inflammatory disorders.

Intestinal hydrolysis and microbial biotransformation of diacetoxyscirpenol-α-glucoside, HT-2-β-glucoside and N-(1-deoxy-d-fructos-1-yl) fumonisin B1 by human gut microbiota in vitro

Fusarium mycotoxins are common contaminants in cereals and often co-occur with plant-derived mycotoxin sugar conjugates. Several of these modified mycotoxins are not degraded in the small intestine and hence carried through to the large intestine where microbial transformation may occur. This study aims to assess the gastrointestinal stability of the trichothecenes HT-2 toxin (HT-2), HT-2-β-glucoside (HT-2-Glc), diacetoxyscirpenol (DAS), DAS-α-glucoside (DAS-Glc) and fumonisin B1 (FB1), N-(1-deoxy-d-fructos-1-yl) fumonisin-B1 (NDF-FB1). All tested modified mycotoxins were stable under upper gastrointestinal (GI) conditions. In faecal batch culture experiments, HT-2-Glc was hydrolysed efficiently and no further microbial biotransformation of HT-2 was observed. DAS-Glc hydrolysis was slow and DAS was de-acetylated to 15-monoacetoxyscripenol. NDF-FB1 was hydrolysed at the slowest rate and FB1 accumulation varied between donor samples. Our results demonstrate that all tested modified mycotoxins are stable in the upper GI tract and efficiently hydrolysed by human gut microbiota, thus potentially contributing to colonic toxicity. Hence the microbial biotransformation of any novel modified mycotoxins needs to be carefully evaluated.

Multistarter fermentation of glutinous rice with Fu brick tea: Effects on microbial, chemical, and volatile compositions

A higher fermentation efficiency was achieved, using multistarter fermentation of glutinous rice supplemented with Fu brick tea (FGR-FBT), than when using traditional fermentation. The effects of multistarter fermentation on the microbial, chemical, and volatile compositions were determined. When FBT was incorporated during glutinous rice fermentation, increased population of yeasts and fungi, as well as enhanced α-amylase, proteinase and β-glucosidase activities, were observed. Specific fungi were isolated and identified as Aspergillus spp., which are known to secrete extracellular enzymes that modify the chemical properties, including ethanol levels, pH, total acids, and total soluble solids. The aroma profile of fermented glutinous rice was studied in the absence and presence of FBT, using HS-SPME-GC-MS and the electronic-nose. This analysis indicated that 35 characteristic volatile compounds were only found in FGR-FBT. The results show that FBT can be added during the fermentation of food products to enhance microbial biotransformation and modify flavour metabolism.

Kansuiphorin C and Kansuinin A ameliorate malignant ascites by modulating gut microbiota and related metabolic functions.

Euphorbia kansui is a toxic Chinese herbal medicine and exhibits promising treatment to the malignant ascites (MA) in its traditional use. Ingenane-type and jastrophane-type diterpenes are demonstrated to be responsible for the toxicity and efficacy of kansui. Two representative compounds, kansuiphorin C (KPC) and kansuinin A (KA) in each type were proved to effectively reduce the ascites. The biological and toxicological effects are closely associated with the gastrointestinal tract, but the possible mechanism and related metabolic functions of KPC and KA treating MA through modulating the gut microbiota remain unclear. To investigate the possible mechanism and related metabolism of KPC and KA ameliorating malignant ascites through modulating gut microbiota. MA rats and normal rats were divided into different groups and administrated with KPC, KA, and positive drug, respectively. 16S rDNA gene sequencing and metagenomes analysis combined with the quantification of short-chain fatty acids of feces were performed to reflect the modulation of gut microbiota. Then, the metabolites of KPC and KA in rat feces under the normal and pathological circumstances were detected by ultra-fast liquid chromatography coupled with MS/MS detector (UFLC-MS/MS) to explore the in-vivo bacterial biotransformation. KPC and KA were modulatory compounds for gut microbiota. The richness of Lactobacillus and the decreased abundance of Helicobacter involved in the carbohydrate metabolism and amino acid metabolism could be responsible for their prohibitory effects on malignant ascites. KPC exhibited stronger modulation of gut microbiota through making the abundance of Helicobacter about 3.5 times lower than KA. Besides, in-vivo microbial biotransformation of KPC and KA contained oxidation, hydrolysis, dehydration, and methylation to form metabolites of lower polarity. Besides, at the dosage of 10mgkg-1, the toxicity of both compounds had weaker influences on the gut microbiota of normal rats. KPC and KA could ameliorate malignant ascites by modulating gut microbiota mainly containing the increase of Lactobacillus and the decrease of Helicobacter and related carbohydrate and amino acid metabolism, providing a basis for their promising clinical usage.

Microbial biotransformation of N-nitro-, C-nitro-, and C-nitrous-type mutagens by Lactobacillus delbrueckii subsp. bulgaricus in meat products

Processed meats are classified by the International Agency for Research on Cancer (IARC) as carcinogenic to humans. However, information on the responsible agents and the influence of industrial processing on the increased risk of cancer is still lacking. This study aimed to use cultures of Lactobacillus delbrueckii subsp. bulgaricus LB-UFSC 01 to biodegrade harmful C-nitrous, N-nitro, and C-nitro compounds in processed meat matrix. Firstly, positive results for ethylnitrolic acid (ENA) (>5.00 μg kg−1) and 2-methyl-1,4-dinitro-pyrrole (DNMP) (>12.0 μg kg−1) were obtained in mortadellas produced under different experimental conditions employing preservatives and antioxidants. Mortadellas containing nitrite and sorbate in the ratio of 8:1 (w/w) yielded the highest concentrations of mutagens. However, the treatment with the LB-UFSC 01 culture was able to modulate the harmful compounds in the mortadella samples. Several analytical methods employing liquid chromatography coupled to mass spectrometry and statistical models were employed to identify the metabolites and reaction routes during microbial biotransformation. For the first time, relevant information regarding the formation and degradation of ENA and DNMP in a processed meat model simulating real conditions was presented.

Diamondoids are not forever: microbial biotransformation of diamondoid carboxylic acids.

SummaryOil sands process‐affected waters (OSPW) contain persistent, toxic naphthenic acids (NAs), including the abundant yet little‐studied diamondoid carboxylic acids. Therefore, we investigated the aerobic microbial biotransformation of two of the most abundant, chronically toxic and environmentally relevant diamondoid carboxylic acids: adamantane‐1‐carboxylic acid (A1CA) and 3‐ethyl adamantane carboxylic acid (3EA). We inoculated into minimal salts media with diamondoid carboxylic acids as sole carbon and energy source two samples: (i) a surface water sample (designated TPW) collected from a test pit from the Mildred Lake Settling Basin and (ii) a water sample (designated 2 m) collected at a water depth of 2 m from a tailings pond. By day 33, in TPW enrichments, 71% of A1CA and 50% of 3EA was transformed, with 50% reduction in EC20 toxicity. Similar results were found for 2 m enrichments. Biotransformation of A1CA and 3EA resulted in the production of two metabolites, tentatively identified as 2‐hydroxyadamantane‐1‐carboxylic acid and 3‐ethyladamantane‐2‐ol respectively. Accumulation of both metabolites was less than the loss of the parent compound, indicating that they would have continued to be transformed beyond 33 days and not accumulate as dead‐end metabolites. There were shifts in bacterial community composition during biotransformation, with Pseudomonas species, especially P. stutzeri, dominating enrichments irrespective of the diamondoid carboxylic acid. In conclusion, we demonstrated the microbial biotransformation of two diamondoid carboxylic acids, which has potential application for their removal and detoxification from vast OSPW that are a major environmental threat.

Anti-Inflammatory Effects of Formononetin 7-O-phosphate, a Novel Biorenovation Product, on LPS-Stimulated RAW 264.7 Macrophage Cells.

Biorenovation is a microbial enzyme-catalyzed structural modification of organic compounds with the potential benefits of reduced toxicity and improved biological properties relative to their precursor compounds. In this study, we synthesized a novel compound verified as formononetin 7-O-phosphate (FMP) from formononetin (FM) using microbial biotransformation. We further compared the anti-inflammatory properties of FMP to FM in lipopolysaccharide (LPS)-treated RAW264.7 macrophage cells. We observed that cell viabilities and inhibitory effects on LPS-induced nitric oxide (NO) production were greater in FMP-treated RAW 264.7 cells than in their FM-treated counterparts. In addition, FMP treatment suppressed the production of proinflammatory cytokines such as prostaglandin-E2 (PGE2), interleukin-6 (IL-6), and interleukin-1β (IL-1β) in a dose-dependent manner and concomitantly decreased the mRNA expression of inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2). We also found that FMP exerted its anti-inflammatory effects through the downregulation of the extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and nuclear factor kappa B (NF-κB) signaling pathways. In conclusion, we generated a novel anti-inflammatory compound using biorenovation and demonstrated its efficacy in cell-based in vitro assays.

Maximizing the Efficiency of Vanillin Production by Biocatalyst Enhancement and Process Optimization.

The rising demand of bio-vanillin and the possibility to use microbial biotransformation to produce this compound from agroindustrial byproducts are economically attractive. However, there are still several bottlenecks, including substrate and product toxicity, formation of undesired products and genetic stability of the recombinant strains, that impede an efficient use of recombinant Escherichia coli strains to make the whole process cost effective. To overcome these problems, we developed a new E. coli strain, named FR13, carrying the Pseudomonas genes encoding feruloyl-CoA synthetase and feruloyl-CoA hydratase/aldolase integrated into the chromosome and, using resting cells, we demonstrated that the vanillin yield and selectivity were strongly affected by the physiological state of the cells, the temperature used for the growth and the recovery of the biomass and the composition and pH of the bioconversion buffer. The substrate consumption rate and the vanillin yield increased using a sodium/potassium phosphate buffer at pH 9.0 as bioconversion medium. Optimization of the bioprocess variables, using response surface methodology, together with the use of a two-phase (solid-liquid) system for the controlled release of ferulic acid allowed us to increase the vanillin yield up to 28.10 ± 0.05 mM. These findings showed that recombinant plasmid-free E. coli strains are promising candidates for the production of vanillin at industrial scale and that a reduction of the cost of the bioconversion process requires approaches that minimize the toxicity of both ferulic acid and vanillin.

Transport and Biotransformation of Gliclazide and the Effect of Deoxycholic Acid in a Probiotic Bacteria Model.

Introduction: Inter-individual differences in gut microflora composition may affect drug metabolism and overall therapeutic response. Gliclazide is a drug characterized by large inter-individual differences in therapeutic response; however, the causes of these differences are not fully explained and may be the outcome of microbial biotransformation. Recently, great attention has been paid to studies on bile acid (BA) interactions with gut microflora and the role of BAs in the modification of drug transport through biological membranes.The Aim: Considering the assumption of gliclazide–probiotic–BAs interactions, the aim of the study was to investigate the transport and biotransformation of gliclazide in probiotic bacteria, as well as the effects of deoxycholic acid (DCA) on gliclazide transport into bacterial cells.Materials and Methods: Probiotics were incubated with gliclazide with or without DCA for 24 h at 37°C. The intracellular and extracellular concentrations of gliclazide were determined at seven time points by high-performance liquid chromatography. Gliclazide biotransformation by the enzymatic activity of probiotic bacteria was examined using appropriate software packages.Results: During the 24 h incubation with probiotic bacteria, significantly lower extracellular concentrations of gliclazide were observed at all time points compared to controls, while in the group with DCA, the decrease in concentration was noticed only at 24 h. The total concentration of gliclazide throughout the whole period was significantly lower compared to control. Proposed pathways of gliclazide biotransformation by probiotic bacteria involve reactions of hydrolysis and hydroxylation.Conclusion: Based on the results obtained, it can be concluded that there are interactions of gliclazide–probiotics–DCA, at both the level of active and passive transport into the cells, and at the level of drug biotransformation by enzymatic activity of probiotic bacteria. The effect of these interactions on the final therapeutic response of gliclazide should be further studied and confirmed in in vivo conditions.

A highly sensitive graphene oxide based label-free capacitive aptasensor for vanillin detection

Biosynthetic production of vanillin via microbial biotransformation offers a low-cost alternative for manufacturers to meet the consumer demands for natural vanillin. However, identifying the high vanillin-producing microbial strains among multitudinous samples using the current analytical techniques such as liquid chromatography (LC) and mass spectroscopy (MS) is time consuming, cumbersome and costly. Here, we propose an alternative low-cost and rapid aptamer-based capacitive assay for sensitive and selective vanillin recognition based on the preferential binding affinity and stability of the aptamer-vanillin complex. This redox-free approach measures the changes in non-faradaic capacitance of transducing graphene-oxide (GO) activated gold electrodes immobilized with vanillin-specific aptamer. Aptamer-vanillin interaction on the GO surface alters the aptamer conformation causing surface charge redistribution detected via capacitance-frequency characteristics. The aptasensor showed a wide dynamic detection range of 10 pM-10 nM and a low limit of detection (LOD) of ~9.91 pM, which is the best reported so far. Finally, validation of the capacitive aptasensing against high-performance LC (HPLC) reference containing vanillin dissolved in a complex M9 medium with interfering compounds (ferulic acid and glycerol), to mimic typical microbial biotransformation, demonstrated good sensitivity and selectivity. The successful proof-of-concept can be translated to high-throughput electronic multi-analyte screening kits supplementary to existing analytical tools.

Production of 14α-hydroxysteroids by a recombinant Saccharomyces cerevisiae biocatalyst expressing of a fungal steroid 14α-hydroxylation system.

The 14α-hydroxysteroids have specific anti-gonadotropic and carcinolytic biological activities and can be produced by microbial biotransformation. The steroid 11β-/14α-hydroxylase P-450lun from Cochliobolus lunatus is the only fungal cytochrome P450 enzyme identified to date with steroid C14 hydroxylation ability. Previous work has mainly revealed the 11β-hydroxylation activity of the P-450lun towards cortexolone (RSS) substrate; however, the potential steroid 14α-hydroxylation activity of this enzyme, especially for androstenedione (AD) substrate, has not yet conducted in-depth testing. In this work, we further tested the steroid 14α-hydroxylation activity of the P-450lun towards RSS and AD in the Saccharomyces cerevisiae system. We demonstrated that P-450lun functions as the specific 14α-hydroxylase towards the AD substrate (regiospecificity > 99%); however, it showed a poor C14-hydroxylation regiospecificity (around 40%) for the RSS substrate. In addition, through transcriptome analysis combined with gene functional characterizations, we also identified and cloned the gene for the P-450lun-associated redox partner CPRlun. Finally, through codon optimization, knockout of genes for the side reactions related enzymes GCY1 and YPR1, and increasing copies of the P-450lun and CPRlun, we developed a recombinant S. cerevisiae biocatalyst based on the C. lunatus steroid 14α-hydroxylation system to produce 14α-hydroxysteroids. Initial production of 14α-OH-AD (150 mg/L day productivity, 99% regioisomeric purity, and 60% w/w yield) and 14α-OH-RSS (64 mg/L day productivity, 40% regioisomeric purity, and 26% w/w yield) were separately achieved in shake flasks; these results represent the highest level of 14α-hydroxysteroid production in the current yeast system.

Effects of phenotypic variations on the microbial hydroxylation of fatty acids by Pseudomonas sp. NRRL B-2994

Hydroxy fatty acids (HFAs) are highly valued industrial materials. Pseudomonas sp. NRRL B-2994 was used for stereospecific microbial biotransformation to hydroxylate unsaturated fatty acids (UFAs). As Pseudomonas sp. was continuously subcultured, the hydroxylation capability (both conversion rate and productivity) decreased. A morphology change was observed from large to small colonies. To produce stereospecific 10-hydroxy-12(Z)-octadecenoic acid from plant oils by using Pseudomonas sp. NRRL B-2994, the effect of phenotypic variations related to microbial hydroxylation of UFAs was confirmed. The conversion rate and the total productivity of creating HFAs from UFAs by microbial hydroxylation were highly dependent upon colony phenotype variations of Pseudomonas sp. NRRL B-2994. The morphological change was responsible for a lower rate of hydroxylation. The small colony variants showed increased hydrophobicity of the cell surface resulting in cell aggregation in liquid culture and lower hydroxylation due to limited exposure of substrates, UFAs. Small colony variants could be reverted to typical large colony variants. An economically feasible process was established for microbial hydroxylation using large colony variants with 50% HFA conversion rate and 10-15g/L of productivity.

Transformation of polyphenols found in pigmented gluten-free flours during in vitro large intestinal fermentation

In this work, 18 gluten-free flours (prepared from cereals, pseudocereals and legumes), differing in pigmentation, were screened for their phenolic profiles, cooked and, then, subjected to digestion and large intestinal fermentation in vitro. A combined targeted/untargeted metabolomic approach was used to elucidate the microbial biotransformation processes of polyphenols following digestion. This preliminary work demonstrated an increase in 3,5-dihydroxybenzoic acid (on average from 0.67 up to 1.30 μmol/g dry matter) throughout large intestinal fermentation of pseudocereals (esp. quinoa), due to their high alkylresorcinol contents. Isoflavones were converted into equol- or O-desmethylangolensin- derivatives, whereas anthocyanins were degraded into lower-molecular-weight phenolics (i.e., protocatechuic aldehyde and 4-hydroxybenzoic acid, with the latter exhibiting the highest increase over time). A decreasing trend was observed for antioxidant activities (i.e., FRAP and ORAC values) moving from digested to faecal fermented samples. These findings highlight that gluten-free flours are able to deliver bioaccessible polyphenols to the colon.