Improvement of bioactive metabolite production in microbial cultures-A systems approach by OSMAC and deconvolution-based 1 HNMR quantification

Enhancing chemical and biological diversity by co-cultivation

In natural product research, microbial metabolites have tremendous potential to provide new therapeutic agents since extremely diverse chemical structures can be found in the nearly infinite microbial population. Conventionally, these specialized metabolites are screened by single-strain cultures. However, owing to the lack of biotic and abiotic interactions in monocultures, the growth conditions are significantly different from those encountered in a natural environment and result in less diversity and the frequent re-isolation of known compounds. In the last decade, several methods have been developed to eventually understand the physiological conditions under which cryptic microbial genes are activated in an attempt to stimulate their biosynthesis and elicit the production of hitherto unexpressed chemical diversity. Among those, co-cultivation is one of the most efficient ways to induce silenced pathways, mimicking the competitive microbial environment for the production and holistic regulation of metabolites, and has become a golden methodology for metabolome expansion. It does not require previous knowledge of the signaling mechanism and genome nor any special equipment for cultivation and data interpretation. Several reviews have shown the potential of co-cultivation to produce new biologically active leads. However, only a few studies have detailed experimental, analytical, and microbiological strategies for efficiently inducing bioactive molecules by co-culture. Therefore, we reviewed studies applying co-culture to induce secondary metabolite pathways to provide insights into experimental variables compatible with high-throughput analytical procedures. Mixed-fermentation publications from 1978 to 2022 were assessed regarding types of co-culture set-ups, metabolic induction, and interaction effects.

Combination of GC-MS Molecular Networking and Larvicidal Effect against Aedes aegypti for the Discovery of Bioactive Substances in Commercial Essential Oils

Dengue is a neglected disease, present mainly in tropical countries, with more than 5.2 million cases reported in 2019. Vector control remains the most effective protective measure against dengue and other arboviruses. Synthetic insecticides based on organophosphates, pyrethroids, carbamates, neonicotinoids and oxadiazines are unattractive due to their high degree of toxicity to humans, animals and the environment. Conversely, natural-product-based larvicides/insecticides, such as essential oils, present high efficiency, low environmental toxicity and can be easily scaled up for industrial processes. However, essential oils are highly complex and require modern analytical and computational approaches to streamline the identification of bioactive substances. This study combined the GC-MS spectral similarity network approach with larvicidal assays as a new strategy for the discovery of potential bioactive substances in complex biological samples, enabling the systematic and simultaneous annotation of substances in 20 essential oils through LC50 larvicidal assays. This strategy allowed rapid intuitive discovery of distribution patterns between families and metabolic classes in clusters, and the prediction of larvicidal properties of acyclic monoterpene derivatives, including citral, neral, citronellal and citronellol, and their acetate forms (LC50 < 50 µg/mL).

Microorganisms: the secret agents of the biosphere, and their key roles in biotechnology

Abstract We present a survey of projects that have been funded by FAPESP under the BIOTA-Microorganisms program. These projects generated a wide variety of results, including the identification of novel antibacterial-producing microorganisms, the characterization of novel microbial enzymes for industrial applications, taxonomic classification of novel microorganisms in several environments, investigation of the soil and mangrove microbial ecosystems and its influence on endangered plant species, and the sequencing of novel metagenome-assembled genomes. The results surveyed demonstrate the importance of microorganisms in environments that play important roles in human activities as well as the potential that many of these microorganisms have in contributing to biotechnological applications crucial for human survival in the 21st century.

Use of elicitors to enhance or activate the antibiotic production in streptomyces

Streptomyces is the largest and most significant genus of Actinobacteria, comprising 961 species. These Gram-positive bacteria produce many versatile and important bioactive compounds; of these, antibiotics, specifically the enhancement or activation of their production, have received extensive research attention. Recently, various biotic and abiotic elicitors have been reported to modify the antibiotic metabolism of Streptomyces, which promotes the production of new antibiotics and bioactive metabolites for improvement in the yields of endogenous products. However, some elicitors that obviously contribute to secondary metabolite production have not yet received sufficient attention. In this study, we have reviewed the functions and mechanisms of chemicals, novel microbial metabolic elicitors, microbial interactions, enzymes, enzyme inhibitors, environmental factors, and novel combination methods regarding antibiotic production in Streptomyces. This review has aimed to identify potentially valuable elicitors for stimulating the production of latent antibiotics or enhancing the synthesis of subsistent antibiotics in Streptomyces. Future applications and challenges in the discovery of new antibiotics and enhancement of existing antibiotic production using elicitors are discussed.

Induction of metabolic variability of the endophytic fungus Xylaria sp. by OSMAC approach and experimental design

This work has as the main focus, to analyze the behavior of physic-chemical variations from the fungus Xylaria sp., through the OSMAC (One Strain, Many Compounds) approach as an efficient way of obtaining new compounds. To perform such inductions and to explore the variability of the metabolic network of this microorganism, a factorial design was designed to induce variability (or enhancement) of metabolites. In view of chemometric insights, the planned inductions were imposed on the microorganism and variations in the chemical profile were observed in the crude extracts. Through mass spectrometry (HR-ESI-MS) and nuclear magnetic resonance-based profiles, combined with multivariate analysis through Principal Component Analysis (PCA), it was observed a marked variability of signals, confirming the efficacy in the metabolic alteration, defining the culture medium and agitation as the most important variables in the metabolic variability of the fungus. However, the extract mass is more significant for the agitation variable, and there is no relationship between the mass of crude extract and the amount of molecular signals of the complex matrices studied.

Limonoids and other triterpenoids from Entandrophragma angolense

Four new compounds (1-4) were isolated from the stem bark of Entandrophragma angolense along with eleven known structures (5-15). The chemical structures were elucidated on the basis of spectroscopic and HRMS data, and the absolute configuration was established with the aid of electronic circular dichroism. Compound 5 displayed moderate cytotoxicity against MDA-MB-231, OVCAR3, MDA-MB-435, and HT29 cell lines, with IC₅₀ values ranging from 2.0-5.9 μM.

Fungal benzene carbaldehydes: occurrence, structural diversity, activities and biosynthesis

Covering: up to April 2020Fungal benzene carbaldehydes with salicylaldehydes as predominant representatives carry usually hydroxyl groups, prenyl moieties and alkyl side chains. They are found in both basidiomycetes and ascomycetes as key intermediates or end products of various biosynthetic pathways and exhibit diverse biological and pharmacological activities. The skeletons of the benzene carbaldehydes are usually derived from polyketide pathways catalysed by iterative fungal polyketide synthases. The aldehyde groups are formed by direct PKS releasing, reduction of benzoic acids or oxidation of benzyl alcohols.

Highly Oxygenated Constituents from a Marine Alga-Derived Fungus Aspergillus giganteus NTU967

Agar-based disc diffusion antimicrobial assay has shown that the ethyl acetate extract of the fermented broth of Aspergillusgiganteus NTU967 isolated from Ulva lactuca exhibited significant antimicrobial activity in our preliminary screening of bioactive fungal strains. Therefore, column chromatography of the active principles from liquid- and solid–state fermented products of the fungal strain was carried out, and which had led to isolation of eleven compounds. Their structures were determined by spectral analysis to be seven new highly oxygenated polyketides, namely aspergilsmins A–G (1–7), along with previously reported patulin, deoxytryptoquivaline, tryptoquivaline and quinadoline B. Among these, aspergilsmin C (3) and patulin displayed promising anticancer activities against human hepatocellular carcinoma SK-Hep-1 cells and prostate cancer PC-3 cells with IC₅₀ values between 2.7–7.3 μM. Furthermore, aspergilsmin C (3) and patulin exhibited significant anti-angiogenic functions by impeding cell growth and tube formation of human endothelial progenitor cells without any cytotoxicity.