Optimisation de la production de métabolites secondaires à intérêt Thérapeutique par Penicillium sp.

The need for safer natural alternative treatments has increased due to antibiotic resistance and the ineffectiveness of conventional treatments for chronic diseases such as diabetes and polyarthritis. Fungi are renowned for their ability to produce active secondary metabolites that can be used in the development of effective medicines for human health. This research is the subject of an initial study in Algeria, which focused on examining the mycochemical profile and investigating the biological activities of ethyl acetate (EtOAc) extracts of Penicillium isolates isolated from different, mainly extreme, environments. A total of six fungal strains were identified and selected on the basis of their morphological and molecular characteristics: Penicillium bilaiae EWB-3, Penicillium citrinum PB1, Penicillium hordei PA2, Penicillium sp. 3 PM2, Penicillium sp. 2 PM6, Penicillium sp. 1 PM7. Anti-microbial activity was tested by the well method against several Gram-positive and Gram-negative bacteria, a yeast and a mould pathogenic to humans. All the extracts tested were active against Staphylococcus aureus ATCC 43306 and Methicillin-Resistant Staphylococcus aureus ATCC 43300, with significant zones of inhibition of 24 and 25 mm. The contents of total phenols (TPC), flavonoids (TFC) and tannins (TTC) were estimated by colorimetric methods. The high antioxidant potential of fungal ethyl acetate extracts was determined by the DPPH, FRAP, ABTS, Phenantroline, SNP and FIC free radical scavenging tests, confirming their high phenol, flavonoid and tannin content. Assessment of in vitro anti-inflammatory activity using the bovine serum albumin (BSA) denaturation method gave very encouraging results for all EtOAc extracts, except for the PM7 extract, which did not show any anti-inflammatory activity. Using the alpha amylase inhibition method, the results showed that the EWB-3, PB1 and PA2 extracts had significant anti-diabetic activity. Evaluation of the anti-cancer activity of extracts EWB-3, PB1, PA2, using the MTT test, showed an average cytotoxic activity of all extracts against HeLa cells. EWB-3 extract was the most biologically active during in vitro tests, possessing significant antimicrobial activity against C. albicans, S. aureus and E. faecalis with inhibition zone diameters of 31, 26 and 25 mm, respectively. This extract also showed very promising anti-oxidant, antiinflammatory, anti-diabetic and anti-cancer properties, with IC50 values of 45.93, 2.67, 23.07 and 50 µg/ml respectively. Optimisation of the culture parameters to increase the production of antimicrobial agents gave satisfactory results with a stirring speed of 200 rpm and a pH of 4.5. The chromatographic techniques used to determine the presence of natural bioactive molecules in fungal EtOAc extracts from Penicillium strains are: gas chromatography coupled to mass spectrometry (GC-MS) and high performance liquid chromatography (HPLC), various important metabolites isolated for the first time in fungi were obtained, such as Erigeside B, Amorfrutine A, chlorozotocine, 14-Epiandrographolide, Yohimban-17-one, propanoic acid, Fumigaclavine C, Brevianamide F, which could be a promising source of secondary metabolites with potent pharmacological activity. Key words: Penicillium, bioactive metabolites, anti-microbial activity, anti-inflammatory activity, anti-oxidant activity, anti-diabetic activity, anti-cancer activity

Contribution à l’étude de la biodégradation des déchets plastiques par les champignons

Environmental pollution due to the accumulation of plastic waste constitutes a major ecological problem. The degradation of these polymers in the environment depends on the presence of microorganisms capable of decomposing them in their ecosystem. The objective of this study is to determine the contribution and effectiveness of indigenous soil fungi in the degradation of low-density polyethylene (LDPE) plastic bag films, a very common plastic waste in nature. In this regard, nine fungal species were isolated on PDA (Potato-Dextrose-Agar) medium after 7 days of incubation at 27°C. These isolates were collected from the public landfill of Boumehadier located in the city of Collo in the east of Skikda (Algeria). Five species were selected for biodegradation tests and were identified through phylogenetic analysis as Aspergillus niger, Rhizopus arrhizus, Penicillium hordei, Candida tropicalis, and Rhodotorula mucilaginosa. The degradation potential was studied in vitro in batch cultures, in a liquid minimal medium (MML) by acting on several parameters, such as temperature, pH, and fungal biomass, in order to optimize biodegradation. Furthermore, other tests were conducted in vitro in a continuous culture and ex situ in different natural environments (seawater, tap water, and a soil sample). The degradation rates obtained after optimization are respectively 17.21%, 23.77%, 7.77%, 7.60%, and 5.53% for A. niger, R. arrhizus, P. hordei, C. tropicalis, and R. mucilaginosa after one month of incubation. However, low degradation rates (less than 1%) were obtained for films incubated ex situ with P. hordei, C. tropicalis, and R. mucilaginosa, unlike films incubated with A. niger and R. arrhizus showing degradation rates higher than 1% in natural environments. As for the continuous culture, higher weight loss percentages were found, up to 29.74% after three months of incubation with R. arrhizus. The biodegradation was confirmed by scanning electron microscopy (SEM), which revealed several alterations such as surface cracks of the films incubated with fungal species, unlike control films showing smooth surfaces without apparent changes. Furthermore, biological hydrolysis and oxidation activities of LDPE films were revealed by Fourier-transform infrared spectroscopy (FTIR), showing various structural modifications including the appearance of functional groups such as esters, aldehydes, and ketones, presenting carbonyl groups. Finally, X-ray diffraction (XRD) showed peaks of high intensity at the angular position 2θ = 20 - 30° confirming the semi-crystalline structure of the tested polymers. Moreover, several alterations were observed after degradation by fungal isolates, including intensity variations and shifts in the position of certain peaks. This study highlights the effectiveness of the identified isolates in LDPE degradation. These fungal species show promise for applications in plastic polymer biodegradation, which could be exploited to develop future mycoremediation systems. Keywords: Biodegradation, fungi, continuous culture, plastic waste, ex situ, in vitro, LDPE, pollution.