Biochemistry of lipolytic enzymes secreted by Penicillium solitum and Cladosporium cladosporioides

Rigid bioplastics shape the microbial communities involved in the treatment of the organic fraction of municipal solid waste

While bioplastics are gaining wide interest in replacing conventional plastics, it is necessary to understand whether the treatment of the organic fraction of municipal solid waste (OFMSW) as an end-of-life option is compatible with their biodegradation and their possible role in shaping the microbial communities involved in the processes. In the present work, we assessed the microbiological impact of rigid polylactic acid (PLA) and starch-based bioplastics (SBB) spoons on the thermophilic anaerobic digestion and the aerobic composting of OFMSW under real plant conditions. In order to thoroughly evaluate the effect of PLA and SBB on the bacterial, archaeal, and fungal communities during the process, high-throughput sequencing (HTS) technology was carried out. The results suggest that bioplastics shape the communities' structure, especially in the aerobic phase. Distinctive bacterial and fungal sequences were found for SBB compared to the positive control, which showed a more limited diversity. Mucor racemosus was especially abundant in composts from bioplastics' treatment, whereas Penicillium roqueforti was found only in compost from PLA and Thermomyces lanuginosus in that from SBB. This work shed a light on the microbial communities involved in the OFMSW treatment with and without the presence of bioplastics, using a new approach to evaluate this end-of-life option.

Future climate change enhances the complexity of plastisphere microbial co-occurrence networks, but does not significantly affect the community assembly

Biobased and biodegradable plastics have been intensively used in agriculture as mulching films. They provide a distinctive habitat for soil microbes, yet much less is known about the community assembly and interactions of plastisphere microbiota in soils under future climate change. For the first time, we explored the relative importance of ecological processes and the co-occurrence networks of plastic-associated microbes under ambient and future climates. The drift primarily dominated the community assembly of bacteria and fungi after 180D and 328D incubation in both climate regimes. The neutral community model prediction indicated that the migration rate of the plastisphere community in the later decay phase was lower than that in the early decay phase, contributing to the generation of the specific niches. Furthermore, future climate promoted the complexity and modularity of plastic-associated microbial networks: more competition and cooperation were observed in bacteria (or inter-kingdom) and fungi under future climate conditions, respectively. Overall, our findings strengthened the understanding of ecological processes and interplay of plastisphere microbiota during plastic biodegradation in soils under ambient and future climate regimes.

Back to the Future: Decomposability of a Biobased and Biodegradable Plastic in Field Soil Environments and Its Microbiome under Ambient and Future Climates

Decomposition by microorganisms of plastics in soils is almost unexplored despite the fact that the majority of plastics released into the environment end up in soils. Here, we investigate the decomposition process and microbiome of one of the most promising biobased and biodegradable plastics, poly(butylene succinate-co-adipate) (PBSA), under field soil conditions under both ambient and future predicted climates (for the time between 2070 and 2100). We show that the gravimetric and molar mass of PBSA is already largely reduced (28-33%) after 328 days under both climates. We provide novel information on the PBSA microbiome encompassing the three domains of life: Archaea, Bacteria, and Eukarya (fungi). We show that PBSA begins to decompose after the increase in relative abundances of aquatic fungi (Tetracladium spp.) and nitrogen-fixing bacteria. The PBSA microbiome is distinct from that of surrounding soils, suggesting that PBSA serves as a new ecological habitat. We conclude that the microbial decomposition process of PBSA in soil is more complex than previously thought by involving interkingdom relationships, especially between bacteria and fungi.

Studying the Gene Expression of Penicillium rubens Under the Effect of Eight Essential Oils

Essential oils (EOs) are well-known for their beneficial properties against a broad range of microorganisms. For the better understanding of their mechanism of action in fungi, a microarray approach was used in order to evaluate the gene expression of Penicillium chrysogenum (recently renamed P. rubens) exposed to the indirect contact (vapors) of eight EOs. The selection of assayed EOs was based on their antifungal activity. The extraction of RNA and the microarray hybridization procedure were optimized for the analysis of P. rubens. Gene ontology annotation was performed to investigate the functional analysis of the genes. To uncover the metabolic pathway of these differentially expressed genes, they were mapped into the KEGG BRITE pathway database. The transcriptomic analysis showed that, from a total of 12,675 genes, only 551 genes are annotated, and the other 12,124 genes encoded hypothetical proteins. Further bioinformatic analysis demonstrated that 1350 genes were upregulated and 765 downregulated at least with half (four) of the utilizing EOs. A microarray investigation has confirmed the main impact of EOs to metabolic processes in P. rubens involved in vital functions. Presumably, this is the first time that a microarray hybridization analysis was performed in order to evaluate the gene expression of P. rubens exposed to various EOs.

Stability and structure of Penicillium chrysogenum lipase in the presence of organic solvents

The present work describes the enzymatic properties of Penicillium chrysogenum lipase and its behavior in the presence of organic solvents. The temperature and pH optima of the purified lipase was found to be 55 °C and pH 8.0 respectively. The lipase displayed remarkable stability in both polar and non-polar solvents upto 50% (v/v) concentrations for 72 h. A structural perspective of the purified lipase in different organic solvents was gained by using circular dichroism and intrinsic fluorescence spectroscopy. The native lipase consisted of a predominant α-helix structure which was maintained in both polar and non-polar solvents with the exception of ethyl butyrate where the activity was decreased and the structure was disrupted. The quenching of fluorescence intensity in the presence of organic solvents indicated the transformation of the lipase microenviroment P. chrysogenum lipase offers an interesting system for understanding the solvent stability mechanisms which could be used for rationale designing of engineered lipase biocatalysts for application in organic synthesis in non-aqueous media.

An alkaline and surfactant-tolerant lipase from Trichoderma lentiforme ACCC30425 with high application potential in the detergent industry

Alkaline lipases with adaptability to low temperatures and strong surfactant tolerance are favorable for application in the detergent industry. In the present study, a lipase-encoding gene, TllipA, was cloned from Trichoderma lentiforme ACCC30425 and expressed in Pichia pastoris GS115. The purified recombinant TlLipA was found to have optimal activities at 50 °C and pH 9.5 and retain stable over the pH range of 6.0–10.0 and 40 °C and below. When using esters of different lengths as substrates, TlLipA showed preference for the medium length p-nitrophenyl octanoate. In comparison to commercial lipases, TlLipA demonstrated higher tolerance to various surfactants (SDS, Tween 20, and Triton X100) and retained more activities after incubation with Triton X100 for up to 24 h. These favorable characteristics make TlLipA prospective as an additive in the detergent industry.

Penicillium salamii strain ITEM 15302: A new promising fungal starter for salami production

Traditional sausages are often considered of superior quality to sausages inoculated with commercial starter cultures and this is partially due to the action of the typical house microflora. Penicillium nalgiovense is the species commonly used as starter culture for dry-cured meat production. Recently a new species, Penicillium salamii, was described as typical colonizer during salami seasoning. In order to understand its contribution to the seasoning process, two different experiments on curing of fresh pork sausages were conducted using P. salamii ITEM 15302 in comparison with P. nalgiovense ITEM 15292 at small and industrial scale, and the dry-cured sausages were subjected to sensory analyses. Additionally, proteolytic and lipolytic in vitro assays were performed on both strains. P. salamii ITEM 15302 proved to be a fast growing mould on dry-cured sausage casings, well adapted to the seasoning process, with high lipolytic and proteolytic enzymatic activity that confers typical sensory characteristics to meat products. Therefore, P. salamii ITEM 15302 was shown to be a good candidate as new starter for meat industry.

Fungi Isolated from Maize (Zea mays L.) Grains and Production of Associated Enzyme Activities

Filamentous fungi produce a great variety of enzymes, and research on their biotechnological potential has recently intensified. The objective of this work was to identify, at the species level, using DNA barcoding, 46 fungal isolates obtained from maize grains with rot symptoms. We also analyzed the production of extracellular amylases, cellulases, proteases and lipases of 33 of those fungal isolates. The enzymatic activities were evaluated by the formation of a clear halo or a white precipitate around the colonies in defined substrate media. The found fungi belong to the genera Talaromyces, Stenocarpella, Penicillium, Phlebiopsis, Cladosporium, Hyphopichia, Epicoccum, Trichoderma, Aspergillus, Irpex, Fusarium, Microdochium, Mucor and Sarocladium. In the genus Fusarium, the species Fusarium verticillioides was predominant and this genus presented the highest diversity, followed by the genera Aspergillus. The best genera for lipase production were Cladosporium and Penicillium; while Cladosporium, Aspergillus and Penicillium were best for cellulase activity; Hyphopichia, Aspergillus and Irpex for amylase activity; and Cladosporium and Sarocladium for proteases activity. In conclusion, a collection of fungi from maize seeds presenting rotten symptoms were obtained, among which exist important producers of hydrolases.