Germanane Monolayer Films as Antibacterial Coatings

Germanane (GeH), a graphane analogue, has attracted significant interest because of its optoelectronic properties; however, the environmental and biological effects of GeH have scarcely been investigated so far. Here we report a facile approach based on the Langmuir-Schaefer deposition to produce homogeneous and dense GeH monolayer films on various substrates. In view of possible applications and to extend the use of GeH to unexplored fields, we investigated its antibacterial activity for the first time and found that this promising 2D structure exhibits remarkable antibacterial activity against both Gram-negative and Gram-positive bacterial strains

Hybrid Nanomaterials of Magnetic Iron Nanoparticles and Graphene Oxide as Matrices for the Immobilization of beta-Glucosidase:Synthesis, Characterization, and Biocatalytic Properties

Hybrid nanostructures of magnetic iron nanoparticles and graphene oxide were synthesized and used as nanosupports for the covalent immobilization of β-glucosidase. This study revealed that the immobilization efficiency depends on the structure and the surface chemistry of nanostructures employed. The hybrid nanostructure-based biocatalysts formed exhibited a two to four-fold higher thermostability as compared to the free enzyme, as well as an enhanced performance at higher temperatures (up to 70°C) and in a wider pH range. Moreover, these biocatalysts retained a significant part of their bioactivity (up to 40%) after 12 repeated reaction cycles

Production, purification and characterization of thermostable hemicellulases

In the present Thesis, the hemicellulolytic system of the thermophilic fungi Chaetomium thermophilum IMI 291753, Thermomyces lanuginosus IMI 84400 and Sporotrichum thermophile ATCC 34628 was studied with regard to the optimization and characterization of xylanase production. Subsequently, the isolation, purification and characterization of β-xylosidase and endoxylanase from S. thermophile ATCC 34628 were accomplished. The optimization of xylanase production was based on a 32 central composite experimental design. The parameters studied were carbon and nitrogen sources. A second-order quadratic model and a response surface methodology were used to predict the optimum conditions for xylanase production. The results obtained here were confirmed by the experimental results that followed. In all cases, the raw materials for optimization trials were agro-industrial by-products of low cost, such as corn cob and wheat straw. The xylanase production optimization was followed by their characterization concerning thermostability and pH optimum. The characteristics of xylanases from all three fungi were proved to be hopeful for potential industrial applications. The ability of the enzyme produced by C. thermophilum IMI 291753 to be active in high pH values could be very useful for the treatment of alkaline pulps. Thermostable cellulase-free xylanase was produced by T. lanuginosus IMI 84400. The xylanase production was comparable to the production reported for other xylanase hyperproducing microorganisms and for different strains of the same microorganism, as well. Taking into account that low cost industrial wastes have been used as raw materials, the production of this xylanase would decrease the cost of production in an environmentally sound manner. Finally, two of the hemicellulolytic enzymes from S. thermophile ATCC 34628 were purified and characterized during this study: An extracellular endoxylanase and an intracellular β-xylosidase. The characterization of the two enzymes was made with regard to the molecular weight, thermostability, pH optimum, pI, specificity and inhibition. Based on the catalytic properties and the partial subsite mapping, the endo-xylanase purified from S. thermophile ATCC 34628 can be classified in family 11 of glycosyl hydrolases.Στην παρούσα διατριβή μελετάται το σύστημα ημικυτταρινασών από τους θερμόφιλους μύκητες Chaetomium thermophilum IMI 291753, Thermomyces lanuginosus IMI 84400 και Sporotrichum thermophile ATCC 34628. Η μελέτη περιλαμβάνει αρχικά την αριστοποίηση της παραγωγής και τον χαρακτηρισμό των ξυλανασών και στη συνέχεια, την απομόνωση και τον καθαρισμό μίας εξ’ αυτών καθώς και μιας β-ξυλοζιδάσης από τον S. thermophile ATCC 34628. Για την αριστοποίηση της παραγωγής των ξυλανασών από τους θερμόφιλους μύκητες C. thermophilum IMI 291753, T. lanuginosus IMI 84400 και S. thermophile ATCC 34628, κατά τη διάρκεια της καλλιέργειάς τους σε βυθισμένη καλλιέργεια χρησιμοποιήθηκε κεντρικός σχεδιασμός αστέρα 32. Οι αρχικές παράμετροι που μελετήθηκαν ήταν οι πηγές άνθρακα και αζώτου. Τα αποτελέσματα χρησιμοποιήθηκαν για την κατασκευή δευτεροβάθμιων γραμμικών μοντέλων. Μέσω αυτών των μοντέλων έγινε η πρόβλεψη των βέλτιστων συνθηκών για την παραγωγή των ξυλανασών με τη μέθοδο της επιφανειακής απόκρισης. Για κάθε μοντέλο το θεωρητικό βέλτιστο επαληθεύτηκε πειραματικά με πολύ ικανοποιητική προσέγγιση. Σε όλες τις περιπτώσεις, η παραγωγή των ημικυτταρινασών από τους τρεις μύκητες πραγματοποιήθηκε από αγροτοβιομηχανικά παραπροϊόντα, δηλαδή από εξαιρετικά φθηνές πρώτες ύλες όπως ο σπάδικας αραβοσίτου και το άχυρο σίτου. Την αριστοποίηση των συνθηκών παραγωγής των ξυλανασών ακολούθησε ο χαρακτηρισμός τους αναφορικά με την θερμοσταθερότητά τους και το βέλτιστο pH δράσης τους. Οι ξυλανάσες των τριών μικροοργανισμών παρουσίασαν χαρακτηριστικά ελπιδοφόρα για την βιομηχανική παραγωγή και εκμετάλλευσή τους. Η ικανότητα του ενζύμου από τον C. thermophilum IMI 291753 να δρα σε αλκαλικό pH, θα μπορούσε να βρει εφαρμογή στην κατεργασία αλκαλικών πολτών στη χαρτοβιομηχανία. Οι θερμοάντοχες ξυλανάσες, ελεύθερες κυτταρινασών, παράγονται από τον T. lanuginosus IMI 84400 σε παραγωγή συγκρίσιμη με την παραγωγή τους τόσο από άλλα στελέχη του ίδιου μικροοργανισμού, όσο και από άλλους υπερθερμόφιλους μικροοργανισμούς. Το γεγονός αυτό σε συνδυασμό με τις φθηνές πρώτες ύλες θα μπορούσε να συμβάλλει στη μείωση του κόστους της βιομηχανικής τους παραγωγής με φιλικό προς το περιβάλλον τρόπο. Τέλος, στα πλαίσια αυτής της διατριβής, πραγματοποιήθηκε η απομόνωση, ο χαρακτηρισμός και η μελέτη δύο ημικυτταρινολυτικών ενζύμων του S. thermophile ATCC 34628, μίας ενδοξυλανάσης και μίας β-ξυλοζιδάσης. Τα δύο ένζυμα μελετήθηκαν αναφορικά με το μοριακό τους βάρος, τη θερμοανθεκτικότητά τους, το βέλτιστο pH, το ισοηλεκτρικό τους σημείο, την εξειδίκευσή τους και τους αναστολείς τους. Τα αποτελέσματα της μελέτης για την απομονωμένη ενδοξυλανάση δείχνουν ότι το ένζυμο αυτό έχει παρόμοιες καταλυτικές ιδιότητες με ένζυμα που ανήκουν στην οικογένεια 11 των γλυκοϋδρολασών

Exopolysaccharide Production in Submerged Fermentation of <i>Pleurotus ostreatus</i> under Red and Green Light

Light controls the developmental, physiological, morphological, and metabolic responses of many fungi. Most fungi respond primarily to blue, red, and green light through their respective photoreceptors. In this study, a screening of different light wavelengths’ effects on submerged Pleurotus ostreatus cultivation in baffled flasks was conducted. P. ostreatus growth was not inhibited in all tested conditions, while an equal or higher protein content was observed in comparison with dark conditions. Red and green light favored exopolysaccharide (EPS) production while red and blue light favored intracellular polysaccharide (IPS) production. To focus on EPS production, the effect of red and green light wavelengths on the production of the polysaccharide via submerged cultivation of P. ostreatus LGAM 1123 was tested. Submerged cultivation using red light in baffled flasks resulted in EPS production of 4.1 ± 0.4 g/L and IPS content of 23.1 ± 1.4% of dry weight (dw), while green light resulted in EPS production of 4.1 ± 0.2 g/L and 44.8 ± 5.2% dw IPS content. Similar production levels were achieved in a 3.5 L bioreactor using red light. The EPS produced using red light revealed a polysaccharide with a higher antioxidant activity compared to the polysaccharides produced by green light. In addition, the analysis of the crude polysaccharides has shown differences in biochemical composition. The structural differences and β glucan’s existence in the crude polysaccharides were confirmed by FT-IR analysis. Overall, these polysaccharides could be used in the food industry as they can enhance the functional health-promoting, physicochemical, and sensory properties of food products

Laccase and Biomass Production via Submerged Cultivation of <i>Pleurotus ostreatus</i> Using Wine Lees

Large quantities of wine lees are produced annually by the wine industry. The high phenolic content makes them unsuitable for disposal in the environment or animal feed without a suitable treatment. In this study, wine lees were treated by Pleurotus ostreatus in submerged cultivation, producing a high-value biomass and elevated levels of laccase, an important industrial enzyme. Biomass and laccase production reached 21 g/L and 74,000 Units/L, respectively, at the optimal conditions of initial pH 6.0, 20% v/v wine lees, 30 g/L glucose, and 20 g/L yeast extract, while decolorization and dephenolization rates of the waste were over 90%. The mycelial biomass was rich in proteins and essential amino acids reaching up to 43% and 16% per dry weight, respectively. Carbohydrates and lipids were the second richest bioactive compound in biomass, with values of 29.4 ± 2.7% and 29.5 ± 2.7%, respectively. The crude laccase in the culture supernatant was purified via a simple two-step purification procedure by 4.4-fold with a recovery of 44%. The molecular weight of the enzyme was determined to be 62 kDa via SDS electrophoresis. Enzyme activity was optimal at pH 5.0 and 70 °C. The activation energy of the enzyme was calculated at a value of 20.0 ± 0.2 kJ/mol. The pH stability and thermostability of the purified laccase were studied. The enzyme was remarkably stable at pH 8.0 and at temperatures up to 40 °C. The thermal inactivation energy of the enzyme was determined to be 76.0 ± 1.2 kJ/mol. The thermodynamic parameters (ΔH*, ΔG*, and ΔS*) for the thermal deactivation of the purified laccase at a temperature range of 20–60 °C were: 73.8 ≤ ΔH* ≤ 74.3 kJ·mol−1, 98.7 ≤ ΔG* ≤ 101.9 kJ·mol−1, and −90.5 ≤ ΔS* ≤ −84.3 J·mol−1·K−1. Wine lees could be ideal substrates of fungal cultivation for laccase production and biomass with a high protein content in an eco-friendlier way

Benefits of supplementation with microbial omega-3 fatty acids on human health and the current market scenario for fish-free omega-3 fatty acid

BackgroundGrowing evidence points to a link between specific fatty acids ingested through the diet and human health. Chain length, saturation degree, and position of double bonds in fatty acids determine their effect in humans. Omega-3 and omega-6 fatty acids have been recognized for their contribution to the prevention and/or treatment of diabetes, cancer, visual impairment, cardiovascular diseases, as well as neurological and musculoskeletal disorders. Scope and approachHumans cannot synthesize these fatty acids in sufficient amounts and need to absorb them through the diet. Oleaginous microalgae constitute a promising, sustainable source of such fatty acids, as they can accumulate up to 85% of lipids on a cell dry weight basis. Key findings and conclusionsThe present review summarizes the potential of oleaginous microalgae as a convenient, economical, and sustainable source of polyunsaturated fatty acids, and explores their beneficial role in human health. The growing prevalence of cardiovascular diseases and changing dietary preferences are driving the increasing demand for microbial omega-3 fatty acids. Following the COVID-19 pandemic, the importance of a healthy immune system has further strengthened the market for omega-3 fatty acids.Validerad;2023;Nivå 2;2023-05-12 (hanlid);Funder: Hellenic Foundation for Research and Innovation (HFRI) and the General Secretariat for Research and Technology (GSRT) (1137)Green and sustainable approach to valorise high saline and oily fish processing effluents for production of nutraceuticalsBoosting the squalene content in thraustochytrids by genetic engineering using CRISPR–Cas9 System to replace shark-based squalene as an adjuvant for COVID 2019 vaccin

Heterotrophic Cultivation of the Cyanobacterium <i>Pseudanabaena</i> sp. on Forest Biomass Hydrolysates toward Sustainable Biodiesel Production

Environmental pollution, greenhouse gas emissions, depletion of fossil fuels, and a growing population have sparked a search for new and renewable energy sources such as biodiesel. The use of waste or residues as substrates for microbial growth can favor the implementation of a biorefinery concept with reduced environmental footprint. Cyanobacteria constitute microorganisms with enhanced ability to use industrial effluents, wastewaters, forest residues for growth, and concomitant production of added-value compounds. In this study, a recently isolated cyanobacterium strain of Pseudanabaena sp. was cultivated on hydrolysates from pretreated forest biomass (silver birch and Norway spruce), and the production of biodiesel-grade lipids was assessed. Optimizing carbon source concentration and the (C/N) carbon-to-nitrogen ratio resulted in 66.45% w/w lipid content when microalgae were grown on glucose, compared to 62.95% and 63.79% w/w when grown on spruce and birch hydrolysate, respectively. Importantly, the lipid profile was suitable for the production of high-quality biodiesel. The present study demonstrates how this new cyanobacterial strain could be used as a biofactory, converting residual resources into green biofuel