Penicillium roqueforti : a multifunctional cell factory of high value-added molecules

The Mutually Inspiring Biological and Chemical Synthesis of Fungal Bicyclo[2.2.2]diazaoctane Indole Alkaloids

Fungal indole alkaloids bearing a bicyclo[2.2.2]diazaoctane (BCDO) core structure are a fascinating family of natural products that exhibit a wide spectrum of biological activities. These compounds also display remarkable structural diversity, with many different diastereomers and enantiomers produced by specific fungal strains. The biogenesis of the unique BCDO moiety has long been proposed to involve an intramolecular [4+2] hetero-Diels-Alder (IMDA) reaction, but the exact mechanisms for this hypothetical transformation have remained elusive until recently. This review aims to summarize the whole history of synthetic and biosynthetic studies of fungal BCDO indole alkaloids, by covering the discovery, biomimetic syntheses, total syntheses, biosynthetic pathway elucidation, and biological activities of representative compounds. We highlight the mutual inspiration and corroboration between biological and synthetic chemists in exploring the intriguing biosynthetic mysteries of this family of natural products. We also provide perspectives and clues for the remaining biosynthetic problems.

Structural alteration of cocoa bean shell fibers through biological treatment using Penicillium roqueforti

Lignocellulosic residues, such as cocoa bean shell (FI), are generated in large quantities during agro-industrial activities. Proper management of residual biomass through solid state fermentation (SSF) can be effective in obtaining value-added products. The hypothesis of the present work is that the bioprocess promoted by P. roqueforti can lead to structural changes in the fibers of the fermented cocoa bean shell (FF) that confer characteristics of industrial interest. To unveil such changes, the techniques of FTIR, SEM, XRD, TGA/TG were used. After SSF, an increase of 36.6% in the crystallinity index was observed, reflecting the reduction of amorphous components such as lignin in the FI residue. Furthermore, an increase in porosity was observed through the reduction of the 2θ angle, which gives the FF a potential candidate for applications of porous products. The FTIR results confirm the reduction in hemicellulose content after SSF. The thermal and thermogravimetric tests showed an increase in the hydrophilicity and thermal stability of FF (15% decomposition) in relation to the by-product FI (40% decomposition). These data provided important information regarding changes in the crystallinity of the residue, existing functional groups and changes in degradation temperatures.

Cocoa bean shells: a review into the chemical profile, the bioactivity and the biotransformation to enhance their potential applications in foods

During processing, cocoa bean shells (CBS) are de-hulled from the bean and discarded as waste. Undermined by its chemical and bioactive composition, CBS is abundant in dietary fiber and phenolic compounds that may serve the valorization purpose of this by-product material into prebiotic and functional ingredients. In addition, the cell-wall components of CBS can be combined through enzymatic feruloylation to obtain feruloylated oligo- and polysaccharides (FOs), further enhancing the techno-functional properties. FOs have attracted scientific attention due to their prebiotic, antimicrobial, anti-inflammatory and antioxidant functions inherent to their structural features. This review covers the chemical and bioactive compositions of CBS as well as their modifications upon cocoa processing. Physical, chemical, and enzymatic approaches to extract and bio-transform bioactive components from the cell wall matrix of CBS were also discussed. Although nonspecific to CBS, studies were compiled to investigate efforts done to extract and produce feruloylated oligo- and polysaccharides from the cell wall materials.

Biotransformation of artemisinic acid to bioactive derivatives by endophytic Penicillium oxalicum B4 from Artemisia annua L

As a biosynthetic precursor of the antimalarial drug artemisinin, artemisinic acid (AA) is abundant in Artemisia annua L. with a content of 8-10-fold higher than artemisinin, but less effective. In this study, the biotransformation of AA was carried out with an endophytic fungus Penicillium oxalicum B4 to extend its utility. After 10-day-culture of the endophyte with AA at 2 mg/mL, eight biotransformation metabolites were isolated from the culture broth, including five undescribed metabolites, namely 3α,14-dihydroxyartemisinic acid, 14-hydroxy-3-oxo-artemisinic acid, 15-hydroxy-3-oxo-artemisinic acid, 12, 15-artemisindioic acid and 1,2,3,6-tetradehydro-12, 15-artemisindioic acid. The fungal enzymes possess the selective capacity to hydroxylate, carbonylate and ketonize the allyl group of AA. The major biotransformation metabolite was the hydroxylated product 3-α-hydroxyartemisinic acid (33.3%) in the cultures of early stage (day 1-6), whereas most of the other biotransformation products were synthesized in the later stage (day 8-10). Compared with AA, some metabolites (3α,14-dihydroxyartemisinic acid, 15-hydroxy-3-oxo-artemisinic acid and 1,2,3,6-tetradehydro-12, 15-artemisindioic acid) possessed stronger cytotoxic activity to the human colon carcinoma cell line (LS174T) and promyelocytic leukemia cell line (HL-60). The metabolites 12, 15-artemisindioic acid and 3-α-hydroxyartemisinic acid exhibited significant inhibitory activity to the lipopolysaccharide-induced nitrite production of RAW 264.7 cells at 10.00 μM and 2.50 μM, respectively. The results demonstrated the potential of fungal endophytes on biotransforming AA to its bioactive derivatives.

Preservation stress resistance of melanin deficient conidia from Paecilomyces variotii and Penicillium roqueforti mutants generated via CRISPR/Cas9 genome editing

Background

The filamentous fungi Paecilomyces variotii and Penicillium roqueforti are prevalent food spoilers and are of interest as potential future cell factories. A functional CRISPR/Cas9 genome editing system would be beneficial for biotechnological advances as well as future (genetic) research in P. variotii and P. roqueforti.

Results

Here we describe the successful implementation of an efficient AMA1-based CRISPR/Cas9 genome editing system developed for Aspergillus niger in P. variotii and P. roqueforti in order to create melanin deficient strains. Additionally, kusA⁻ mutant strains with a disrupted non-homologous end-joining repair mechanism were created to further optimize and facilitate efficient genome editing in these species. The effect of melanin on the resistance of conidia against the food preservation stressors heat and UV-C radiation was assessed by comparing wild-type and melanin deficient mutant conidia.

Conclusions

Our findings show the successful use of CRISPR/Cas9 genome editing and its high efficiency in P. variotii and P. roqueforti in both wild-type strains as well as kusA⁻ mutant background strains. Additionally, we observed that melanin deficient conidia of three food spoiling fungi were not altered in their heat resistance. However, melanin deficient conidia had increased sensitivity towards UV-C radiation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40694-021-00111-w.

Tyrosine Induced Metabolome Alterations of Penicillium roqueforti and Quantitation of Secondary Key Metabolites in Blue-Mold Cheese

To map qualitative and quantitative metabolome alterations when Penicillium roqueforti is grown in an environment where l-tyrosine levels are perturbed, the recently established differential off-line LC-NMR (DOLC-NMR) approach was successfully applied in connection with an absolute metabolite quantitation using a quantitative ¹H NMR protocol following the ERETIC 2 (Electronic REference To access In vivo Concentrations) methodology. Among the 23 influenced metabolites, amino acid degradation products like 2-(4-hydroxyphenyl)acetic acid and 2-(3,4-dihydroxyphenyl)acetic acid underwent a tremendous upregulation in the amino acid perturbed approach. Moreover, the output of secondary metabolites like andrastin A, eremofortin B, and the tetrapeptide d-Phe-l-Val-d-Val-l-Tyr was affected in the case of the presence or absence of the added aromatic amino acid. Furthermore, the isolated secondary metabolites of P. roqueforti have been quantified for the first time in five divergent Penicillium isolates by means of a validated LC-ECHO-MS/MS method. This technique is used to compensate the effect of co-extracted matrix compounds during the analysis and to utilize quasi-internal standards to quantify all metabolites of interest accurately. This screening outlined the great variety between the different fungi of the same species. The metabolite spectra of wild-type fungi included more toxic intermediates compared to a selected fungi used as a starter culture for blue-mold cheese production. In addition, these secondary metabolites were quantified in commercially available white- and blue-mold cheese samples. The main differences between the analyte profiles of white and blue cheeses were linked to the impact of the used starter culture. Specific metabolites detected from P. roqueforti like andrastin A and B or roquefortine C could not be detected in white cheese. Among the blue cheese samples, different metabolite pattern could be observed regarding various P. roqueforti starter cultures.

Functional Metabolome Analysis of Penicillium roqueforti by Means of Differential Off-Line LC-NMR

UPLC-TOF/MS profiling, followed by the recently reported differential off-line LC-NMR (DOLC-NMR) and quantitative ¹H NMR spectroscopy (qHNMR), led to the differential qualitative analysis and accurate quantitation of l-tryptophan-induced metabolome alterations of Penicillium roqueforti, which is typically used in making blue-mold cheese. Among the 24 metabolites identified, two tetrapeptides, namely, d-Phe-l-Val-d-Val-l-Tyr and d-Phe-l-Val-d-Val-l-Phe, as well as cis-bis(methylthio)silvatin, are reported for the first time as metabolites of P. roqueforti. Antimicrobial activity tests showed strong effects of the catabolic l-tryptophan metabolites 3-hydroxyanthranilic acid, anthranilic acid, and 3-indolacetic acid against Saccharomyces cerevisiae, with IC₅₀ values between 15.6 and 24.0 μg/mL, while roquefortine C and cis-bis(methylthio)silvatin inhibited the growth of Gram-negative Escherichia coli and Gram-positive Bacillus subtilis with IC₅₀ values between 30.0 and 62.5 μg/mL.

PR Toxin - Biosynthesis, Genetic Regulation, Toxicological Potential, Prevention and Control Measures: Overview and Challenges

Out of the various mycotoxigenic food and feed contaminant, the fungal species belonging to Penicillium genera, particularly Penicillium roqueforti is of great economic importance, and well known for its crucial role in the manufacturing of Roquefort and Gorgonzola cheese. The mycotoxicosis effect of this mold is due to secretion of several metabolites, of which PR toxin is of considerable importance, with regard to food quality and safety challenges issues. The food products and silages enriched with PR toxin could lead into damage to vital internal organs, gastrointestinal perturbations, carcinogenicity, immunotoxicity, necrosis, and enzyme inhibition. Moreover, it also has the significant mutagenic potential to disrupt/alter the crucial processes like DNA replication, transcription, and translation at the molecular level. The high genetic diversities in between the various strains of P. roqueforti persuaded their nominations with Protected Geographical Indication (PGI), accordingly to the cheese type, they have been employed. Recently, the biosynthetic mechanism and toxicogenetic studies unraveled the role of ari1 and prx gene clusters that cross-talk with the synthesis of other metabolites or involve other cross-regulatory pathways to negatively regulate/inhibit the other biosynthetic route targeted for production of a strain-specific metabolites. Interestingly, the chemical conversion that imparts toxic properties to PR toxin is the substitution/oxidation of functional hydroxyl group (-OH) to aldehyde group (-CHO). The rapid conversion of PR toxin to the other derivatives such as PR imine, PR amide, and PR acid, based on conditions available reflects their unstability and degradative aspects. Since the PR toxin-induced toxicity could not be eliminated safely, the assessment of dose-response and other pharmacological aspects for its safe consumption is indispensable. The present review describes the natural occurrences, diversity, biosynthesis, genetics, toxicological aspects, control and prevention strategies, and other management aspects of PR toxin with paying special attention on economic impacts with intended legislations for avoiding PR toxin contamination with respect to food security and other biosafety purposes.

A critical review of producers of small lactone mycotoxins: patulin, penicillic acid and moniliformin

A very large number of filamentous fungi has been reported to produce the small lactone mycotoxins patulin, penicillic acid and moniliformin. Among the 167 reported fungal producers of patulin, only production by 29 species could be confirmed. Patulin is produced by 3 Aspergillus species, 3 Paecilomyces species, 22 Penicillium species from 7 sections of Penicillium, and one Xylaria species. Among 101 reported producers of penicillic acid, 48 species could produce this mycotoxin. Penicillic acid is produced by 23 species in section Aspergillus subgenus Circumdati section Circumdati, by Malbranchea aurantiaca and by 24 Penicillium species from 9 sections in Penicillium and one species that does not actually belong to Penicillium (P. megasporum). Among 40 reported producers of moniliformin, five species have been regarded as doubtful producers of this mycotoxin or are now regarded as taxonomic synonyms. Moniliformin is produced by 34 Fusarium species and one Penicillium species. All the accepted producers of patulin, penicillic acid and moniliformin were revised according to the new one fungus – one name nomenclatural system, and the most recently accepted taxonomy of the species.

Effect of the solid state fermentation of cocoa shell on the secondary metabolites, antioxidant activity, and fatty acids

During cocoa (Theobroma cacao L.) processing, the accumulated cocoa shell can be used for bioconversion to obtain valuable compounds. Here, we evaluate the effect of solid-state fermentation of cacao flour with Penicillium roqueforti on secondary metabolite composition, phenol, carotenoid, anthocyanin, flavonol, and fatty acids contents, and antioxidant activity. We found that the total concentrations of anthocyanins and flavonols did not change significantly after fermentation and the phenolic compound and total carotenoid concentrations were higher. The fermentation process produced an increase in saponin concentration and antioxidant activity, as well as significant changes in the levels of oleic, linoleic, gamma-linolenic, and saturated fatty acids. Based on our findings, we propose that the reuse of food residues through solid state fermentation is viable and useful.

Biosynthetic gene clusters for relevant secondary metabolites produced by Penicillium roqueforti in blue cheeses

Ripening of blue-veined cheeses, such as the French Bleu and Roquefort, the Italian Gorgonzola, the English Stilton, the Danish Danablu or the Spanish Cabrales, Picón Bejes-Tresviso, and Valdeón, requires the growth and enzymatic activity of the mold Penicillium roqueforti, which is responsible for the characteristic texture, blue-green spots, and aroma of these types of cheeses. This filamentous fungus is able to synthesize different secondary metabolites, including andrastins, mycophenolic acid, and several mycotoxins, such as roquefortines C and D, PR-toxin and eremofortins, isofumigaclavines A and B, and festuclavine. This review provides a detailed description of the main secondary metabolites produced by P. roqueforti in blue cheese, giving a special emphasis to roquefortine, PR-toxin and mycophenolic acid, and their biosynthetic gene clusters and pathways. The knowledge of these clusters and secondary metabolism pathways, together with the ability of P. roqueforti to produce beneficial secondary metabolites, is of interest for commercial purposes.