Abstract Background Activating silent biosynthetic gene clusters (BGCs) in Streptomyces remains a major challenge in harnessing their vast secondary metabolic potential and requires diverse, complementary strategies, including bacterial co-cultivation, heterologous expression, chemical elicitation, modulation of gene expression, and the use of pleiotropic and pathway-specific genetic regulators, such as those influenced by cytosolic copper levels. Previous studies reported that, in S. coelicolor, disruption of the sco2730/2731 copper chaperone–transporter system (Sc-M1 mutant) markedly enhances secondary metabolism. However, this activation is only partially reproduced by antisense knockdown constructs targeting sco2730/sco2731 in S. coelicolor (Sc-M2 mutant) and other species (S. venezuelae, S. albidoflavus). This study investigates the basis of the strong activation observed in Sc-M1, with the aim of exploiting this mechanism for activating silent BGCs in Streptomyces. Results Genomic analysis revealed that, in addition to sco2730/2731 inactivation, the Sc-M1 mutant possesses a spontaneous deletion of both chromosomal ends. Construction of a sco2730 knockout mutant (Δsco2730, also affecting sco2731; Sc-M3 mutant) showed an effect on secondary metabolism comparable to that of the Sc-M2 mutant, and demonstrated that sco2730 disruption increases chromosomal-end instability. Metabolomic analyses showed that inactivation of sco2730/2731 (Sc-M3 mutant) or chromosomal-end deletion (Sc-M4 mutant) individually enhanced secondary metabolism. However, only the combination of Δsco2730 and chromosomal-end deletion (Sc-M5 mutant) approached the extensive metabolic activation observed in Sc-M1, affecting up to 60 secondary-metabolite adducts from 17 biosynthetic pathways. Similar synergistic effects were observed in S. venezuelae, where combined knockdown of the sco2730/2731 orthologues and chromosomal-end deletion strongly modulated secondary metabolism, repressing chloramphenicol production while inducing pikromycin biosynthesis, a typically silent and difficult-to-activate S. venezuelae BGC. Conclusions Simultaneous disruption of the sco2730/31 copper chaperone–transporter system and chromosomal-end deletion synergistically enhance secondary metabolism production in S. coelicolor and S. venezuelae. This combined genetic manipulation provides a novel strategy for the challenging task of activating silent biosynthetic pathways and for potentially discovering new bioactive compounds across Streptomyces species.

Extensive studies associate processed meat products with a higher risk of colorectal cancer, while consumption of plant nutraceuticals has the opposite effect, via the reduction of oxidative stress and mucosal inflammation, gut microbiota modification, and direct effects upon tumor cells. In this work, five different processed meat products have been formulated, containing two carotenoids, two omega-3 fatty acids, catechins, carnosic acid, propyl propane thiosulfonate (PTSO), a postbiotic from Lactiplantibacillus plantarum, and the vitamins α-tocopherol, and ascorbyl palmitate. These functional meat products have been tested in a murine model of colorectal cancer. Tumor development, inflammatory biomarkers, and the impact upon the gut microbiota were quantified. PTSO plus the L. plantarum postbiotic exerted an anti-inflammatory effect. The carotenoids exhibited a potent prebiotic-like effect. The functional meat product containing all nutraceutical compounds used in this study reduced the development of macroscopic colorectal tumors, indicating that a synergy between all these compounds is necessary to achieve potent antitumor effects. These results demonstrate that functional meat products can function as an effective system to deliver nutraceutical compounds to the host and promote disease prevention.

BackgroundDisruptions in the gut-brain-microbiota axis are increasingly linked to psychiatric disorders. While cannabinoids possess immunomodulatory and neuroprotective properties, their impact on the microbial architecture during critical neurodevelopmental periods remains poorly understood. This exploratory study investigated whether adolescent treatment with delta-9-tetrahydrocannabinol (THC), cannabidiol (CBD) or their combination modulates dysbiosis in the maternal immune activation (MIA) rat model of schizophrenia.MethodsPregnant Wistar rats received Poly I:C or saline on gestational day 15. From the offspring of treated rats, eight groups were studied based on phenotype (Saline, MIA) and adolescent treatment (vehicle, CBD, THC, THC +CBD), with caecum contents analyzed via 16S rRNA sequencing.ResultsMIA-offspring exhibited reduced bacterial richness, which was further exacerbated by combined THC + CBD treatment. Notably, CBD was associated with beneficial shifts, including reductions in pro-inflammatory Pseudomonadota, Enterobacteriaceae and Pasteurellaceae. Furthermore, both cannabinoids decreased the pro-inflammatory Bilophila wadsworthia in MIA-offspring while promoting anti-inflammatory, short-chain fatty acid-producing taxa such as Oscillibacter, Roseburia and Prevotellaceae.DiscussionExploratory correlation analyses taken at PND120 revealed that THC and CBD differentially shape microbiotabrain structure and microbiota-brain oxidative/inflammatory relationships in a phenotype-dependent manner, with THC and CBD exerting distinct and sometimes opposing effects on redox and inflammatory status. Our findings highlight the microbiota-modulating potential of THC and CBD in a preclinic model of schizophrenia, underscoring the importance of the gut-brain axis given the high prevalence of adolescent cannabis use and its implications for psychiatric vulnerability.

Leptospirosis is a widespread zoonotic disease where biofilm formation significantly hinders treatment, contributing to chronic infections. This preliminary study evaluated the antimicrobial and antibiofilm properties of four flavonoids—apigenin, xanthohumol, quercetin, and luteolin—against Leptospira santarosai (sv. Guaricura), L. interrogans (sv. Copenhageni and Hardjoprajitno), and L. borgpetersenii (sv. Hardjobovis). Using microdilution methods, quercetin and apigenin exhibited superior antimicrobial activity, reaching MICs of ≤ 0.12 µg/mL for L. santarosai sv. Guaricura. In antibiofilm assays, quercetin was the most effective compound, successfully disrupting biofilm at minimal biofilm disruptive concentrations (MBDC) as low as < 0.0012 µg/µL for L. santarosai sv. Guaricura and for L. interrogans sv. Copenhageni and Hardjoprajitno. These findings highlight the potential therapeutic candidates, requiring further evaluation, for managing both acute and persistent forms of leptospirosis, either alone or as adjuvants to current antibiotic therapies. Further in vivo studies are warranted to confirm their therapeutic safety and clinical efficacy.

Streptomycetes are biotechnologically valuable bacteria with complex cell division that produce extracellular vesicles (EVs), typically nanometre-sized but can reach 2.5 μm in diameter. Streptomyces also produce dividing wall-deficient L-forms (0.5–7 μm diameter) and, under hyperosmotic stress, non-dividing wall-deficient S-cells (3–4 μm diameter). The boundaries between EVs, L-forms and S-cells are not always clear, as large DNA-containing EVs can resemble small L-forms and S-cells in size. Both EVs and wall-deficient cells offer competitive advantages, such as inter-bacterial signalling, antibiotic transport, resistance and phage defence. However, their formation mechanisms remain poorly understood. We identified sco1758 (engA GTPase), sco0954 (methionine N-acetyltransferase), sco4439 (D-Ala-D-Ala carboxypeptidase), and sco4440 (GOLPH3-like) as important for wall-deficient cell formation in Streptomyces coelicolor under hyperosmotic sucrose conditions. Mutations in sco4439 and sco4440 increased tetra–tetra(Gly) and tetra(Gly)–penta(Gly) (4–3) peptidoglycan (PG) dimers, while sco1758 affected only the former. Complementation reversed these changes. sco0954 overexpression enhanced PG-associated methionine acetylation and oxidation. Our findings suggest that PG dimerisation and methionine modification may contribute to the formation of wall-deficient cells under hyperosmotic sucrose stress. Further research is required to elucidate how SCO1758, SCO0954 and SCO4439/40 modulate PG architecture and to evaluate their potential to promote EV production for biotechnological applications.

Cardiovascular disease is the main cause of mortality in industrialized countries, with over 500 million people affected worldwide. In this work, the roles of low-molecular-weight metabolites originating from the gut microbiome, such as short-chain fatty acids, hydrogen sulfide, trimethylamine, phenylacetic acid, secondary bile acids, indoles, different gases, neurotransmitters, vitamins, and complex lipids, are discussed in relation to their CVD-promoting or preventing activities. Molecules of mixed microbial and human hepatic origin, such as trimethylamine N-oxide and phenylacetylglutamine, are also presented. Finally, dietary agents with cardioprotective effects, such as probiotics, prebiotics, mono- and poly-unsaturated fatty acids, carotenoids, and polyphenols, are also discussed. A special emphasis is given to their gut microbiota-modulating properties.

Colorectal cancer stands as the third most prevalent form of cancer worldwide, with a notable increase in incidence in Western countries, mainly attributable to unhealthy dietary habits and other factors, such as smoking or reduced physical activity. Greater consumption of vegetables and fruits has been associated with a lower incidence of colorectal cancer, which is attributed to their high content of fiber and bioactive compounds, such as flavonoids. In this study, we have tested the flavonoids quercetin, luteolin, and xanthohumol as potential antitumor agents in an animal model of colorectal cancer induced by azoxymethane and dodecyl sodium sulphate. Forty rats were divided into four cohorts: Cohort 1 (control cohort), Cohort 2 (quercetin cohort), Cohort 3 (luteolin cohort), and Cohort 4 (xanthohumol cohort). These flavonoids were administered intraperitoneally to evaluate their antitumor potential as pharmaceutical agents. At the end of the experiment, after euthanasia, different physical parameters and the intestinal microbiota populations were analyzed. Luteolin was effective in significantly reducing the number of tumors compared to the control cohort. Furthermore, the main significant differences at the microbiota level were observed between the control cohort and the cohort treated with luteolin, which experienced a significant reduction in the abundance of genera associated with disease or inflammatory conditions, such as Clostridia UCG-014 or Turicibacter. On the other hand, genera associated with a healthy state, such as Muribaculum, showed a significant increase in the luteolin cohort. These results underline the anti-colorectal cancer potential of luteolin, manifested through a modulation of the intestinal microbiota and a reduction in the number of tumors.

Flavonoids are a large and important group of phytochemicals with a great variety of bioactivities. The addition of methyl groups during biosynthesis of flavonoids and other polyphenols enhances their bioactivities and increases their stability. In a previous study of our research group, we detected a novel flavonoid O-methyltransferase activity in Streptomyces albidoflavus J1074, which led to the heterologous biosynthesis of homohesperetin from hesperetin in feeding cultures. In this study, we identify the O-methyltransferase responsible for the generation of this methylated flavonoid through the construction of a knockout mutant of the gene XNR_0417, which was selected after a blast analysis using the sequence of a caffeic acid 3′-O-methyltransferase from Zea mays against the genome of S. albidoflavus J1074. This mutant strain, S. albidoflavus ∆XNR_0417, was no longer able to produce homohesperetin after hesperetin feeding. Subsequently, we carried out a genetic complementation of the mutant strain in order to confirm that the enzyme encoded by XNR_0417 is responsible for the observed O-methyltransferase activity. This new strain, S. albidoflavus SP43-XNR_0417, was able to produce not only homohesperetin from hesperetin, but also different mono-, di-, tri- and tetra-methylated derivatives on other flavanones, flavones and stilbenes, revealing a broad substrate flexibility. Additionally, in vitro experiments were conducted using the purified enzyme on the substrates previously tested in vivo, demonstrating doubtless the capability of XNR_0417 to generate various methylated derivatives.

Background: Regular exercise has been described to modify both the diversity and the relative abundance of certain bacterial taxa. To our knowledge, the effect of a cycling stage race, which entails extreme physiological and metabolic demands, on the gut microbiota composition and its metabolic activity has not been analysed. Objective: The aim of this cohort study was to analyse the dynamics of faecal microbiota composition and short-chain fatty acids (SCFAs) content of professional cyclists over a Grand Tour and their relationship with performance and dietary intake. Methods: 16 professional cyclists competing in La Vuelta 2019 were recruited. Faecal samples were collected at four time points: the day before the first stage (A); after 9 stages (B); after 15 stages (C); and on the last stage (D). Faecal microbiota populations and SCFA content were analysed using 16S rRNA sequencing and gas chromatography, respectively. A principal component analysis (PCA) followed by Generalised Estimating Equation (GEE) models were carried out to explore the dynamics of microbiota and SCFAs and their relationship with performance. Results: Bifidobacteriaceae, Coriobacteriaceae, Erysipelotrichaceae, and Sutterellaceae dynamics showed a strong final performance predictive value (r = 0.83, ranking, and r = 0.81, accumulated time). Positive correlations were observed between Coriobacteriaceae with acetate (r = 0.530) and isovalerate (r = 0.664) and between Bifidobacteriaceae with isobutyrate (r = 0.682). No relationship was observed between SCFAs and performance. The abundance of Erysipelotrichaceae at the beginning of La Vuelta was directly related to the previous intake of complex-carbohydrate-rich foods (r = 0.956), while during the competition, the abundance of Bifidobacteriaceae was negatively affected by the intake of simple carbohydrates from supplements (r = −0.650). Conclusions: An ecological perspective represents more realistically the relationship between gut microbiota composition and performance compared to single-taxon approaches. The composition and periodisation of diet and supplementation during a Grand Tour, particularly carbohydrates, could be designed to modulate gut microbiota composition to allow better performance.

Aromadendrin and taxifolin are two flavanonols (derived from the precursor naringenin) displaying diverse beneficial properties for humans. The carbon skeleton of these flavonoids may be transformed by the human gastrointestinal microbiota into other compounds, like auronols, which exert different and interesting biological activities. While research in flavonoids has become a certainly extensive field, studies about auronols are still scarce. In this work, different versions of the key plant enzyme for flavanonols biosynthesis, The flavanone 3-hydroxylase (F3H), has been screened for selecting the best one for the de novo production of these compounds in the bacterial factory Streptomyces albidoflavus UO-FLAV-004-NAR, a naringenin overproducer strain. This screening has rendered 2.6 μg/L of aromadendrin and 2.1 mg/L of taxifolin final production titers. Finally, the expression of the chalcone isomerase (CHI) from the gut bacterium Eubacterium ramulus has rendered a direct conversion (after feeding experiments) of 38.1% of (+)-aromadendrin into maesopsin and 74.6% of (+)-taxifolin into alphitonin. Moreover, de novo heterologous biosynthesis of 1.9 mg/L of alphitonin was accomplished by means of a co-culture strategy of a taxifolin producer S. albidoflavus and a CHI-expressing Escherichia coli, after the observation of the high instability of alphitonin in the culture medium. This study addresses the significance of culture time optimization and selection of appropriate enzymes depending on the desired final product. To our knowledge, this is the first time that alphitonin de novo production has been accomplished.

Flavonoids exhibit various bioactivities including anti-oxidant, anti-tumor, anti-inflammatory, and anti-viral properties. Methylated flavonoids are particularly significant due to their enhanced oral bioavailability, improved intestinal absorption, and greater stability. The heterologous production of plant flavonoids in bacterial factories involves the need for enough biosynthetic precursors to allow for high production levels. These biosynthetic precursors are malonyl-CoA and l-tyrosine. In this work, to enhance flavonoid biosynthesis in Streptomyces albidoflavus, we conducted a transcriptomics study for the identification of candidate genes involved in l-tyrosine catabolism. The hypothesis was that the bacterial metabolic machinery would detect an excess of this amino acid if supplemented with the conventional culture medium and would activate the genes involved in its catabolism towards energy production. Then, by inactivating those overexpressed genes (under an excess of l-tyrosine), it would be possible to increase the intracellular pools of this precursor amino acid and eventually the final flavonoid titers in this bacterial factory. The RNAseq data analysis in the S. albidoflavus wild-type strain highlighted the hppD gene encoding 4-hydroxyphenylpyruvate dioxygenase as a promising target for knock-out, exhibiting a 23.2-fold change (FC) in expression upon l-tyrosine supplementation in comparison to control cultivation conditions. The subsequent knock-out of the hppD gene in S. albidoflavus resulted in a 1.66-fold increase in the naringenin titer, indicating enhanced flavonoid biosynthesis. Leveraging the improved strain of S. albidoflavus, we successfully synthesized the methylated flavanones hesperetin, homoeriodictyol, and homohesperetin, achieving titers of 2.52 mg/L, 1.34 mg/L, and 0.43 mg/L, respectively. In addition, the dimethoxy flavanone homohesperetin was produced as a byproduct of the endogenous metabolism of S. albidoflavus. To our knowledge, this is the first time that hppD deletion was utilized as a strategy to augment the biosynthesis of flavonoids. Furthermore, this is the first report where hesperetin and homoeriodictyol have been synthesized from l-tyrosine as a precursor. Therefore, transcriptomics is, in this case, a successful approach for the identification of catabolism reactions affecting key precursors during flavonoid biosynthesis, allowing the generation of enhanced production strains.

Flavonoids are a large family of polyphenolic compounds with important agro-industrial, nutraceutical, and pharmaceutical applications. Among the structural diversity found in the flavonoid family, methylated flavonoids show interesting characteristics such as greater stability and improved oral bioavailability. This work is focused on the reconstruction of the entire biosynthetic pathway of the methylated flavones diosmetin and chrysoeriol in Streptomyces albidoflavus. A total of eight different genes (TAL, 4CL, CHS, CHI, FNS1, F3′H/CPR, 3′-OMT, 4′-OMT) are necessary for the heterologous biosynthesis of these two flavonoids, and all of them have been integrated along the chromosome of the bacterial host. The biosynthesis of diosmetin and chrysoeriol has been achieved, reaching titers of 2.44 mg/L and 2.34 mg/L, respectively. Furthermore, an additional compound, putatively identified as luteolin 3′,4′-dimethyl ether, was produced in both diosmetin and chrysoeriol-producing strains. With the purpose of increasing flavonoid titers, a 3-Deoxy-D-arabino-heptulosonic acid 7-phosphate synthase (DAHP synthase) from an antibiotic biosynthetic gene cluster (BGC) from Amycolatopsis balhimycina was heterologously expressed in S. albidoflavus, enhancing diosmetin and chrysoeriol production titers of 4.03 mg/L and 3.13 mg/L, which is an increase of 65% and 34%, respectively. To the best of our knowledge, this is the first report on the de novo biosynthesis of diosmetin and chrysoeriol in a heterologous host.

Vitamin D deficiencies are linked to multiple human diseases. Optimizing its synthesis, physicochemical properties, and delivery systems while minimizing side effects is of clinical relevance and is of great medical and industrial interest. Biotechnological techniques may render new modified forms of vitamin D that may exhibit improved absorption, stability, or targeted physiological effects. Novel modified vitamin D derivatives hold promise for developing future therapeutic approaches and addressing specific health concerns related to vitamin D deficiency or impaired metabolism, such as avoiding hypercalcemic effects. Identifying and engineering key enzymes and biosynthetic pathways involved, as well as developing efficient cultures, are therefore of outmost importance and subject of intense research. Moreover, we elaborate on the critical role that microbial bioconversions might play in the a la carte design, synthesis, and production of novel, more efficient, and safer forms of vitamin D and its analogs. In summary, the novelty of this work resides in the detailed description of the physiological, medical, biochemical, and epidemiological aspects of vitamin D supplementation and the steps towards the enhanced and simplified industrial production of this family of bioactives relying on microbial enzymes. • Liver or kidney pathologies may hamper vitamin D biosynthesis • Actinomycetes are able to carry out 1α- or 25-hydroxylation on vitamin D precursors

This work represents an overview of the current investigations involving organosulfur compounds and colorectal cancer. The molecules discussed in this review have been investigated regarding their impact on colorectal cancer directly, at the in vitro, in vivo, and clinical stages. Organosulfur compounds may have indirect effects on colorectal cancer, such as due to their modulating effects on the intestinal microbiota or their positive effects on intestinal mucosal health. Here, we focus on their direct effects via the repression of multidrug resistance proteins, triggering of apoptosis (via the inhibition of histone deacetylases, increases in reactive oxygen species, p53 activation, β-catenin inhibition, damage in the mitochondrial membrane, etc.), activation of TGF-β, binding to tubulin, inhibition of angiogenesis and metastasis mechanisms, and inhibition of cancer stem cells, among others. In general, the interesting positive effects of these nutraceuticals in in vitro tests must be further analyzed with more in vivo models before conducting clinical trials.

Ulcerative colitis (UC) is a chronic inflammatory disorder affecting the colon, with symptomatology influenced by factors including environmental, genomic, microbial, and immunological interactions. Gut microbiota dysbiosis, characterized by bacterial population alterations, contributes to intestinal homeostasis disruption and aberrant immune system activation, thereby exacerbating the inflammatory state. This study assesses the therapeutic efficacy of intraperitoneal (IP) injected flavonoids (apigenin, luteolin, and xanthohumol) in the reduction of inflammatory parameters and the modulation of the gut microbiota in a murine model of ulcerative colitis. Flavonoids interact with gut microbiota by modulating their composition and serving as substrates for the fermentation into other anti-inflammatory bioactive compounds. Our results demonstrate the effectiveness of luteolin and xanthohumol treatment in enhancing the relative abundance of anti-inflammatory microorganisms, thereby attenuating pro-inflammatory species. Moreover, all three flavonoids exhibit efficacy in the reduction of pro-inflammatory cytokine levels, with luteolin strongly demonstrating utility in alleviating associated physical UC symptoms. This suggests that this molecule is a potential alternative or co-therapy to conventional pharmacological interventions, potentially mitigating their adverse effects. A limited impact on microbiota is observed with apigenin, and this is attributed to its solubility constraints via the chosen administration route, resulting in its accumulation in the mesentery.

Dunaliella tertiolecta RCC6 was cultivated indoors in glass bubble column photobioreactors operated under batch and semi‐continuous regimens and using two different conditions of light and temperature. Biomass was harvested by centrifugation, frozen, and then lyophilized. The soluble material was obtained by sequential extraction of the lyophilized biomass with solvents with a gradient of polarity (hexane, ethyl acetate, and methanol) and its metabolic composition was investigated through nuclear magnetic resonance (NMR) spectroscopy. The effect of light on chlorophyll biosynthesis was clearly shown through the relative intensities of the 1 H NMR signals due to pheophytins. The highest signal intensity was observed for the biomasses obtained at lower light intensity, resulting in a lower light availability per cell. Under high temperature and light conditions, the 1 H NMR spectra of the hexane extracts showed an incipient accumulation of triacylglycerols. In these conditions and under semi‐continuous regimen, an enhancement of β‐carotene and sterols production was observed. The antibacterial and antibiofilm activities of the extracts were also tested. Antibacterial activity was not detected, regardless of culture conditions. In contrast, the minimal biofilm inhibitory concentrations (MBICs) against Escherichia coli for the hexane extract obtained under semi‐continuous regimen using high temperature and irradiance conditions was promising.

The microbiota-gut-brain axis is a complex interconnected system altered in schizophrenia. The antioxidant N-acetylcysteine (NAC) has been proposed as an adjunctive therapy to antipsychotics in clinical trials, but its role in the microbiota-gut-brain axis has not been sufficiently explored. We aimed to describe the effect of NAC administration during pregnancy on the gut-brain axis in the offspring from the maternal immune stimulation (MIS) animal model of schizophrenia. Pregnant Wistar rats were treated with PolyI:C/Saline. Six groups of animals were studied according to the study factors: phenotype (Saline, MIS) and treatment (no NAC, NAC 7 days, NAC 21 days). Offspring were subjected to the novel object recognition test and were scanned using MRI. Caecum contents were used for metagenomics 16S rRNA sequencing. NAC treatment prevented hippocampal volume reduction and long-term memory deficits in MIS-offspring. In addition, MIS-animals showed lower bacterial richness, which was prevented by NAC. Moreover, NAC7/NAC21 treatments resulted in a reduction of proinflammatory taxons in MIS-animals and an increase in taxa known to produce anti-inflammatory metabolites. Early approaches, like this one, with anti-inflammatory/anti-oxidative compounds, especially in neurodevelopmental disorders with an inflammatory/oxidative basis, may be useful in modulating bacterial microbiota, hippocampal size, as well as hippocampal-based memory impairments.

Background Naringenin is an industrially relevant compound due to its multiple pharmaceutical properties as well as its central role in flavonoid biosynthesis. Results On our way to develop Streptomyces albidoflavus J1074 as a microbial cell factory for naringenin production, we have significantly increased the yields of this flavanone by combining various metabolic engineering strategies, fermentation strategies and genome editing approaches in a stepwise manner. Specifically, we have screened different cultivation media to identify the optimal production conditions and have investigated how the additive feeding of naringenin precursors influences the production. Furthermore, we have employed genome editing strategies to remove biosynthetic gene clusters (BGCs) associated with pathways that might compete with naringenin biosynthesis for malonyl-CoA precursors. Moreover, we have expressed MatBC, coding for a malonate transporter and an enzyme responsible for the conversion of malonate into malonyl-CoA, respectively, and have duplicated the naringenin BGC, further contributing to the production improvement. By combining all of these strategies, we were able to achieve a remarkable 375-fold increase (from 0.06 mg/L to 22.47 mg/L) in naringenin titers. Conclusion This work demonstrates the influence that fermentation conditions have over the final yield of a bioactive compound of interest and highlights various bottlenecks that affect production. Once such bottlenecks are identified, different strategies can be applied to overcome them, although the efficiencies of such strategies may vary and are difficult to predict.

Phytophthora cinnamomi is an important plant pathogen responsible for dieback diseases in plant genera including Quercus, Fagus, Castanea, Eucalyptus, and Pinus, among others, all over the world. P. cinnamomi infection exerts tremendous ecological and economic losses. Several strategies have been developed to combat this pathogenic oomycete, including the search for novel anti-oomycete compounds. In this work, a Mediterranean vascular plant, Phlomis purpurea, has been screened for secondary bioactivity against this pathogen. The genus Phlomis includes a group of herbaceous plants and shrubs described as producers of many different bioactive compounds, including several triterpenoids. Triterpenoids are well-known molecules synthesized by plants and microorganisms with potent antioxidant, antitumoral, and antimicrobial activities. We have isolated by HPLC-DAD and characterized by HPLC-MS and NMR two nortriterpenoid compounds (phlomispentaol A and phlomispurtetraolone) from the root extracts of P. purpurea. One of them (phlomispentaol A) is active against the plant pathogenic oomycete P. cinnamomi (based on in vitro inhibition bioassays). Based on their chemical structure and their relationship to other plant triterpenoids, oleanolic acid is proposed to be the common precursor for these molecules. The anti-oomycete activity shown by phlomispentaol A represents a promising alternative to counteract the worldwide-scale damage caused to forest ecosystems by this pathogen.