Description of lipase producing novel yeast species Debaryomyces apis f.a., sp. nov. and a modified pH indicator dye-based method for the screening of lipase producing microorganisms.

Four yeast strains were isolated from the gut of stingless bee, collected in Churdhar, Himachal Pradesh, India. Physiological characterization, morphological examination, and sequence analysis of small subunit ribosomal RNA (18S rRNA) genes, internal transcribed spacer (ITS) region, and D1/D2 domain of the large subunit rRNA gene revealed that the four strains isolated from the gut of stingless bee belonged to the Debaryomyces clade. Strain CIG-23HT showed sequence divergence of 7.5% from Debaryomyces nepalensis JCM 2095T, 7.8% from Debaryomyces udenii JCM 7855T, and Debaryomyces coudertii JCM 2387T in the D1/D2 domain. In the ITS region sequences, strain CIG-23HT showed a 15% sequence divergence from Debaryomyces nepalensis JCM 2095T and Debaryomyces coudertii JCM 2387T. In 18S rRNA gene sequence, the strain CIG-23HT showed 1.14% sequence divergence from Debaryomyces nepalensis JCM 2095 and and Debaryomyces coudertii JCM 2387, and 0.83% sequence divergence from Debaryomyces hansenii NRRL Y-7426. Strain CIG-23HT can utilize more carbon sources than closely related species. The findings suggest that strain CIG-23HT is a novel species of the genus Debaryomyces, and we propose to name it as Debaryomyces apis f.a., sp. nov. The holotype is CBS 16297T, and the isotypes are MTCC 12914T and KCTC 37024T. The MycoBank number of Debaryomyces apis f.a., sp. nov. is MB836065. Additionally, a method using cresol red and Bromothymol blue pH indicator dyes was developed to screen for lipase producers, which is more sensitive and efficient than the currently used phenol red and rhodamine B dye-based screening methods, and avoids the problem of less differentiable zone of hydrolysis.

Clofazimine pKa Determination by Potentiometry and Spectrophotometry: Reverse Cosolvent Dependence as an Indicator of the Presence of Dimers in Aqueous Solutions.

The weakly basic antibiotic and anti-inflammatory drug, clofazimine (CFZ), was first described in 1957. It has been used therapeutically, most notably in the treatment of leprosy. However, the compound is extremely insoluble in aqueous media, and, indeed, there is poor consensus about what its intrinsic solubility is since the reported values range from 0.04 to 11 ng/mL. To understand the speciation and solubilization of CFZ as a function of pH, it is of paramount importance to know the true aqueous pKa. However, there is also poor consensus about the value of the pKa (reported measured values range from 6.08 to 9.11). In the present study, we report the determination of the CFZ ionization constant using two independent techniques. A state-of-the-art potentiometric analysis was performed, drawing on titration data in methanol-water solutions (46-75 wt % MeOH) of CFZ, using the bias-reducing consensus of two different procedures of extrapolating the apparent psKa values to zero cosolvent to approximate the true aqueous pKa as 9.43 ± 0.12 (25 °C, I = 0.15 M reference ionic strength). In parallel, spectrophotometric UV/vis titration data were acquired (250-600 nm at different pH) in 10 mM HEPES buffer solutions containing up to 54 wt % MeOH. The alternating least squares (ALS) method was used in the analysis of the absorbance-pH spectra. Uncharacteristically, the cosolvent UV/vis data in our study showed reverse cosolvent dependence (apparent pKa values increased with increasing cosolvent) which could be explained by a dimerization of the free base. The analysis of UV/vis data obtained from 54 wt % MeOH-water solution containing 20 µM CFZ yielded the apparent pKa 9.51 ± 0.17 (I ≈ 0.005 M). To assess whether self-assembly of CFZ was energetically feasible, density functional theory (DFT) calculations were used to study the putative CFZ dimers in aqueous and methanol media. The DFT-optimized geometries and infrared spectra of CFZ dimers using water and methanol as solvents were calculated and analyzed. Based on the lack of negative frequencies in calculated infrared spectra, it was confirmed that optimized geometries correspond to the true energetic minima. Visual analysis of optimized structures indicates the presence of stacking interactions between two CFZ molecules. The protonation site (the imine nitrogen atom) was determined by 1H NMR spectroscopy.

Co-inoculations of Lachancea thermotolerans with different Hanseniaspora spp.: Acidification, aroma, biocompatibility, and effects of nutrients in wine.

The use of non-Saccharomyces yeast in the winemaking industry and even more their co-inoculations to maximize their growth and to express phenotypic characteristic is gaining more and more relevance. This study aimed to shed light on the biocompatibilities between Lachancea thermotolerans and Hanseniaspora spp., using different types of nutrients and considering the effect on Yeast Assimilable Nitrogen (YAN), at low temperature (16 °C) and medium SO2 (50 mg/L), in white must. L. thermotolerans has been used for its positive effect on pH reduction and Hanseniaspora spp. for improving the sensory profile. The behaviour of these yeasts was evaluated in co-inoculation, always finishing the fermentation with the sequential inoculation of S. cerevisiae. Significant results were obtained on the population count (CFU/mL) in CHROMagar™, with higher populations of Hanseniaspora spp. with respect to L. thermotolerans. Fermentations with L. thermotolerans/H. vineae, showed inhibition of acidification, generating up to 0.41 g/L of lactic acid. On the contrary, a synergistic effect when L. thermotolerans/H. opuntiae was used, achieved 2.44 g/L of lactic acid and a pH reduction of up to 0.16 and always more significant with Nutrient Vit BlancTM. At the same time ethanol concentration decreased by 3.4 % and volatile acidity never exceeded 0.5 g/L. Aromatic composition was analysed and it was found that all fermentations retained more aromatic esters and that on day 7 the amount of 2-phenylethyl acetate was at least 3 times higher in all fermentations compared to the control (Sc + Nutrient Vit BlancTM) which had 5.96 mg/L. Less yellow intensity (-17.3 %) typical of oxidation were observed in all fermentations in which Nutrient Vit BlancTM had been used and in the sensory analysis the co-inoculations with H. vineae generated better scores.

Debaryomyces hansenii F39A as biosorbent for textile dye removal.

Many industries generate a considerable amount of wastewater containing toxic and recalcitrant dyes. The main objective of this research was to examine the biosorption capacity of Reactive Blue 19 and Reactive Red 141 by the Antarctic yeast Debaryomyces hansenii F39A biomass. Some variables, including pH, dye concentration, amount of adsorbent and contact time, were studied. The equilibrium sorption capacity of the biomass increased with increasing initial dye concentration up to 350mg/l. Experimental isotherms fit the Langmuir model and the maximum uptake capacity (qmax) for the selected dyes was in the range of 0.0676-0.169mmol/g biomass. At an initial dye concentration of 100mg/l, 2g/l biomass loading and 20±1°C, D. hansenii F39A adsorbed around 90% of Reactive Red 141 and 50% of Reactive Blue 19 at pH 6.0. When biomass loading was increased (6g/l), the uptake reached up to 90% for Reactive Blue 19. The dye uptake process followed a pseudo-second-order kinetics for each dye system. As seen throughout this research study, D. hansenii has the potential to efficiently and effectively remove dyes in a biosorption process and may be an alternative to other costly materials.

A novel serine protease from pseuderanthemum latifolium B. Hansen: Characterization and fibrino(geno)lytic activities.

Protease (PPL) was isolated from Pseuderanthemum latifolium B. Hansen and had a molecular mass of 70 kDa. The N-terminal sequence of PPL showed 70-80% similarity with of subtilisin-like serine proteases from plants, but it did not show any sequence homology with known plant proteases. Serine protease inhibitors (PMSF, DFP) effectively blocked about 90% of PPL activity. PPL was highly activity at the pH range from 6 to 9 and temperatures from 50 °C to 80 °C, with an optimum at pH 7.0 and temperatures 70 °C. PPL had stability in a variety of pH, temperature, surfactant and oxidizing agents. PPL with concentration of 2.5 µg completely hydrolyzed the Aα-chain of fibrinogen within 5 min and hydrolyzed the Bß and the γ-chain after 10 h. Fibrin also was strong hydrolyzed by PPL with concentration of 0.3 µg. Thus, PPL is a unique serine protease, which it had strong fibrino(geno)lytic activities.

Effect of pH Buffer and Carbon Metabolism on the Yield and Mechanical Properties of Bacterial Cellulose Produced by Komagataeibacter hansenii ATCC 53582.

Bacterial cellulose (BC) is widely used in the food industry for products such as nata de coco. The mechanical properties of BC hydrogels, including stiffness and viscoelasticity, are determined by the hydrated fibril network. Generally, Komagataeibacter bacteria produce gluconic acids in a glucose medium, which may affect the pH, structure and mechanical properties of BC. In this work, the effect of pH buffer on the yields of Komagataeibacter hansenii strain ATCC 53582 was studied. The bacterium in a phosphate and phthalate buffer with low ionic strength produced a good BC yield (5.16 and 4.63 g/l respectively), but there was a substantial reduction in pH due to the accumulation of gluconic acid. However, the addition of gluconic acid enhanced the polymer density and mechanical properties of BC hydrogels. The effect was similar to that of the bacteria using glycerol in another carbon metabolism circuit, which provided good pH stability and a higher conversion rate of carbon. This study may broaden the understanding of how carbon sources affect BC biosynthesis.

A physiological characterization in controlled bioreactors reveals a novel survival strategy for Debaryomyces hansenii at high salinity.

Debaryomyces hansenii is traditionally described as a halotolerant non-conventional yeast and has served as a model organism for the study of osmotolerance and salt tolerance mechanisms in eukaryotic systems for the past 30 years. However, unraveling of D. hansenii's biotechnological potential has always been difficult due to the persistent limitations in the availability of efficient molecular tools described for this yeast. Additionally, there is a lack of consensus and contradictory information along the recent years that limits a comprehensive understanding of its central carbon metabolism, mainly due to a lack of physiological studies in controlled and monitored environments. Moreover, there is little consistency in the culture conditions (media composition, temperature, and pH among others) used by different groups, which makes it complicated when trying to get prevalent conclusions on behavioral patterns. In this work, we present for the first time a characterization of D. hansenii in batch cultivations using highly controlled lab-scale bioreactors. Our findings contribute to a more complete picture of the central carbon metabolism and the external pH influence on the yeast's ability to tolerate high Na+ and K+ concentrations, pointing to a differential effect of both salts, as well as a positive effect in cell performance when low environmental pH values are combined with a high sodium concentration in the media. Finally, a novel survival strategy at very high salinity (2 M) is proposed for this yeast, as well as potential outcomes for its use in industrial biotechnology applications. TAKE AWAY: High salt concentrations stimulate respiration in Debaryomyces hansenii. Sodium exerts a stronger positive impact on cell performance than potassium. µmax is higher at a combination of low pH, high salt, and high temperature. Concentrations of 2 M salt result in slower growth but increased biomass yield. The positive effect of salts is enhanced at low glucose concentration.

Papain immobilization on heterofunctional membrane bacterial cellulose as a potential strategy for the debridement of skin wounds.

We combined the chemical and physical methods of papain immobilization through the aldehyde groups available on oxidized bacterial cellulose (OxBC) to provide high proteolytic activity for future applications as bioactive dressing. Bacterial cellulose (BC) was obtained by the fermentation of Komagataeibacter hansenii in Hestrin-Schramm medium for 5 days, followed by purification and oxidation using NaIO4. Surface response methodology was used to optimize papain immobilization (2%, w/v) for 24 h. The independent variables: pH (3-7) and temperature (5 to 45 °C) were investigated. The mathematically validated optimal conditions of 45 °C and pH 7 had a statistical effect on the immobilization yield (IY) of papain in OxBC (52.9%). These ideal conditions were also used for papain immobilization in BC (unoxidized). The IY of 9.1% was lower than that of OxBC. OxBC-Papain and BC-Papain were investigated using thermal analysis, confocal microscopy, and diffusion testing. The OxBC support exhibited a more interactive chemical structure than the BC support, and was capable of immobilizing papain by covalent bonds (-C-NHR) and adsorption (ion exchange), with 93.3% recovered activity, 49.4% immobilization efficiency, and better thermal stability. Papain immobilized to OxBC by adsorption displayed 53% widespread papain activity. The results indicate the potential of prolonged bioactivity in debrided chronic wounds.

Effect of lyophilization on the bacterial cellulose produced by different Komagataeibacter strains to adsorb epicatechin.

Bacterial cellulose (BC) has been widely used as a model system to investigate the interaction of polyphenols with the polysaccharides of cell walls. In this study, the water absorption ability and the adsorption ability of epicatechin of the never-dried and freeze-dried BC produced by a high-yield Komagataeibacter hansenii strain ATCC 53582 was compared with two normal-yield strains. The structural characteristics of BC were investigated via microscopy observation and mechanical/rheological tests. The 1-butyl-3-methylimidazolium acetate/dimethyl sulfoxide ([BMIM]Ac/DMSO) co-solvent was used to dissolve BC to calculate the degree of polymerization (DP). Results showed that compared with the other two strain, the BC synthesised by ATCC 53582 had a higher cellulose concentration (1.2 wt%) but lower epicatechin adsorption (29 µg/mg under 4 mM, pH 7). Its fibril network collapsed and led to a reduced recovery ratio (86 %) in the compression-relaxation test, which may be due to large DP (2856).

Drug Formulation Impact on Prefilled Syringe Functionality and Autoinjector Performance.

Given the surging interest in developing prefilled syringe and autoinjector combination products, investment in an early compatibility assessment is critical to prevent unwarranted drug/container closure interactions and avoid potential reformulation during late stages of drug development. In addition to the standard evaluation of drug stability, it is important to consider container closure functionality and overall device performance changes over time because of drug-container closure component interaction. This study elucidated the mechanisms that cause changes in syringe glide force over time and the impact on the injection duration. It was an expansion of the previous work, which indicated that drug formulation variables such as formulation excipients and pH affect syringe functionality over time. The current study described an investigative process for troubleshooting prolonged and variable autoinjector injection time caused by an increased syringe glide force variability over time. This increase in glide force variability stems from two root causes, namely plunger dimensional variation and syringe silicone oil change over time. The results demonstrated (a) the underlying factors of silicone oil change in the presence of drug formulation matrices, (b) accelerated stability of syringe glide force as a good indicator of long-term, real-time stability, and (c) that buffer matrix-filled syringes can be used to predict the syringe functionality and stability of drug product-filled syringes. Based on the experimental findings of a variety of orthogonal characterization techniques including contact angle, interfacial tension, and calculation of Hansen solubility parameters, it is proposed that silicone oil change is caused by formulation excipients and a complex set of phenomena summarized as "wet, wash, and delube" processes.

A genuine mycobacterial thermophile: Mycobacterium hassiacum growth, survival and GpgS stability at near-pasteurization temperatures.

Mycobacterium hassiacum is so far the most thermophilic among mycobacteria as it grows optimally at 50 °C and up to 65 °C in a glycerol-based medium, as verified in this study. Since this and other nontuberculous mycobacteria (NTM) thrive in diverse natural and artificial environments, from where they may access and infect humans, we deemed essential to probe M. hassiacum resistance to heat, a strategy routinely used to control microbial growth in water-supply systems, as well as in the food and drink industries. In addition to possibly being a threat in its own right in rare occasions, M. hassiacum is also a good surrogate for studying other NTM species more often associated with opportunistic infection, namely Mycobacterium avium and Mycobacterium abscessus as well as their strictly pathogenic counterparts Mycobacterium tuberculosis and Mycobacterium leprae. In this regard, this thermophilic species is likely to be useful as a source of stable proteins that may provide more detailed structures of potential drug targets. Here, we investigate M. hassiacum growth at near-pasteurization temperatures and at different pHs and also characterize its thermostable glucosyl-3-phosphoglycerate synthase (GpgS), an enzyme considered essential for M. tuberculosis growth and associated with both nitrogen starvation and thermal stress in different NTM species.

Development and evaluation of dapsone tablets coated for specific colon release.

Objective: Drug release systems based on colonic microbiota have been explored with the use of polysaccharides, which are biodegradable. In order to modulate the release into the colon, dapsone tablets were developed, coated with Surelease® and chondroitin sulfate (SC).Methods: The formulation was developed using the wet granulation method, in the form of 9-millimetre circular tablets. The coating was applied in a perforated basin-type coating using different proportions of Surelease® and chondroitin sulfate. The tablets were assessed according to the criteria of mean weight, hardness, and friability. The dissolution test was performed in the dissolver IV apparatus, in media simulating the gastrointestinal system environments (pH 1.2-pH 6.0 and pH 7.2) for 420 min. The results were analyzed by statistical analysis and factorial design.Results: The results of mean weight, hardness, and friability met the pharmacopeial specifications. In the dissolution test, the results obtained demonstrated that Surelease® is able to offer effective protection to the drug, releasing minimum rates when used at 6% or 10% of the tablet's weight gain. The experiments showed that the drug was not able to spread through the coatings manufactured exclusively with Surelease® or even when SC was incorporated in different proportions. Only in the formulation where SC was included in the highest proportion (10%), and the weight gain of the tablet was lower (6%), the release of dapsone increased, reaching 9.5% of drug released. Through factorial planning, it was observed that the drug release rate increases when the weight gain of the tablet remains at the lower level (6%), while the amount of polysaccharide is increased (90:10).Conclusions: The data indicate that the proportion of polysaccharide for ethyl cellulose in the film and the thickness of the coating are the key parameters in controlling the release of the drug from the system.

Molecular characterization and immunogenic function of ML1899 (LipG) of Mycobacterium leprae.

Introduction. ML1899 is conserved in all mycobacterium sp. and is a middle member of mle-ML1898 operon involved in mycolic acid modification.Aim. In the present study attempts were made to characterize ML1899 in detail.Methodology. Bioinformatics tools were used for prediction of active-site residues, antigenic epitopes and a three-dimensional model of protein. The gene was cloned, expressed and purified as His-tagged protein in Escherichia coli for biophysical/biochemical characterization. Recombinant protein was used to treat THP-1 cells to study change in production of nitric oxide (NO), reactive oxygen species (ROS), cytokines and chemokines using flowcytometry/ELISA.Results. In silico analysis predicted ML1899 as a member of α/ß hydrolase family with GXSXG-motif and Ser126, His282, Asp254 as active-site residues that were confirmed by site-directed mutagensis. ML1899 exhibited esterase activity. It hydrolysed pNP-butyrate as optimum substrate at pH 8.0 and 50 °C with 5.56 µM-1 min-1 catalytic efficiency. The enzyme exhibited stability up to 60 °C temperature and between pH 6.0 to 9.0. K m, V max and specific activity of ML1899 were calculated to be 400 µM, 40 µmoles min-1 ml-1 and 27 U mg- 1, respectively. ML1899 also exhibited phospholipase activity. The protein affected the survival of macrophages when treated at higher concentration. ML1899 enhanced ROS/NO production and up-regulated pro-inflammatory cytokines and chemokine including TNF-α, IFN-γ, IL-6 and IL-8 in macrophages. ML1899 was also observed to elicit humoral response in 69 % of leprosy patients.Conclusion. These results suggested that ML1899, an esterase could up-regulate the immune responses in favour of macrophages at a low concentration but kills the THP-1 macrophages cells at a higher concentration.

Changes in microbial composition on the crust by different air flow velocities and their effect on sensory properties of dry-aged beef.

Beef rumps (middle gluteal) were dry aged for 28 days using different air flow velocities of 0, 2.5, and 5 m/s (DA0, DA2.5, and DA5, respectively). The microbial composition, physicochemical traits (moisture, pH, and shear force), flavor compounds (inosine 5'-monophosphate, reducing sugar, free amino acid, and free fatty acid), and electronic tongue profile were analyzed at day 0, 14, and 28. No molds or yeasts were detected until day 14. On day 28, Pilaira anomala was found to be the most abundant in DA0, whereas DA2.5 and DA5 showed increased composition of Debaryomyces hansenii. With that, the significant changes in physicochemical traits and flavor compounds occurred. In addition, the pattern of flavor compounds and taste attributes from DA0, which had different mold and yeast compositions, were discriminable from DA2.5 and DA5. Therefore, our results suggest that air flow can affect microbial composition on the crust, possibly resulting in different sensory properties of dry-aged beef.

pH-responsive chitosan based hydrogels affect the release of dapsone: Design, set-up, and physicochemical characterization.

Dapsone (DAP) is a bactericidal agent used in the treatment of leprosy, caused by Mycobacterium leprae. Despite its therapeutic potential, DAP has low solubility, which results in allow therapeutic index and a high microbial resistance. Recently, new approaches were used to increase the DAP solubility. In particular, the use of interpenetrating polymer network (IPN)-hydrogels based chitosan (CS) for the controlled release of DAP provides some advantages because they can modify their swelling properties and network structures as a response to environmental stimuli. The aim of this study was to synthesize and physicochemically characterize pH-responsive chitosan/polymer hydrogels to control the release of DAP. For this reason, different combination of polymers, such as polyvinyl pyrrolidone, polyethylene glycol and hydroxypropyl methylcellulose, and concentrations of the cross-linking agents (glutaraldehyde) were used and then blended to the CS. The resulting hydrogels were evaluated in terms of physicochemical and swelling properties, rheological analysis and in vitro release of DAP at different pHs (1.2-6.8). Hydrogels were further characterized by Fourier transformed infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM) analysis. pH-responsive DAP-loaded hydrogels may represent the set-up for developing potential oral formulations for the treatment of leprosy caused by Mycobacterium leprae.

Cheese yeasts.

Numerous traditionally aged cheeses are surface ripened and develop a biofilm, known as the cheese rind, on their surfaces. The rind of such cheeses comprises a complex community of bacterial and fungal species that are jointly responsible for the typical characteristics of the various cheese varieties. Surface ripening starts directly after brining with the rapid colonization of the cheese surface by yeasts. The initially dominant yeasts are acid and salt-tolerant and are capable of metabolizing the lactate produced by the starter lactic acid bacteria and of producing NH3 from amino acids. Both processes cause the pH of the cheese surface to rise dramatically. This so-called deacidification process enables the establishment of a salt-tolerant, Gram-positive bacterial community that is less acid-tolerant. Over the past decade, knowledge of yeast diversity in cheeses has increased considerably. The yeast species with the highest prevalence on surface-ripened cheeses are Debaryomyces hansenii and Geotrichum candidum, but up to 30 species can be found. In the cheese core, only lactose-fermenting yeasts, such as Kluyveromyces marxianus, are expected to grow. Yeasts are recognized as having an indispensable impact on the development of cheese flavour and texture because of their deacidifying, proteolytic, and/or lipolytic activity. Yeasts are used not only in the production of surface-ripened cheeses but also as adjunct cultures in the vat milk in order to modify ripening behaviour and flavour of the cheese. However, yeasts may also be responsible for spoilage of cheese, causing early blowing, off-flavour, brown discolouration, and other visible alterations of cheese.

Salinity and high pH affect energy pathways and growth in Debaryomyces hansenii.

The physiological behavior of Debaryomyces hansenii in response to saline stress and elevated pH was studied. The combination of 1 M NaCl salt and pH 8.0 was required to produce significant changes in the lag phase of growth and a consequent effect on viability. pH 8.0 in the absence or presence of 1 M NaCl produced changes in physiological functions such as respiration, acidification, rubidium transport, transmembrane potential, and fermentation. Our data indicated a stimulation of the H+-ATPase of the plasma membrane at pH 8.0, which increased the transmembrane potential and favored the entry of Na+; this effect was intensified in the presence of NaCl, so the increased energy expenditure resulting from H+ pumping and the extrusion of excess Na+ affected viability. The gene expression pattern studied by microarrays of cells incubated under saline conditions and high pH revealed a down-regulation in genes related to energy-producing pathways and in some genes involved in the cell cycle and DNA transcription, confirming our experimental hypothesis. Although D. hansenii can tolerate high pH and high salt concentrations, its physiological behavior, is better at pH 6.0 and in the absence of sodium; thus, it is an alkali-halotolerant yeast and not a halophilic yeast as previously proposed by other authors.

Purification, characterization and in vivo biocontrol efficiency of killer toxins from Debaryomyces hansenii strains.

Nowadays, the biological control of various yeast and mold pathogens that cause diseases in humans, animals, and plants is an increasing of interest. The discovery of novel agents allows prevention of infectious diseases and post-harvest losses reported every year. In the study, we aimed to investigate the production, purification, and characterization as well as in vivo biocontrol efficiency of killer toxins produced by Debaryomyces hansenii strains TEM8 and TEM17. The molecular mass of the killer toxins was 31.5 kDa and they showed high stability at pHs between 2.5 and 5.5 and up to 37 °C. Their internal amino acid sequences matched the DEHA2G18766g (CAG90862.1) from D. hansenii CBS767, which is similar to Saccharomyces cerevisiae YGR282C BGL2 endo-beta-1,3-glucanase. The yeasts and their purified killer toxins significantly inhibited the growth of plant pathogenic fungi Alternaria brassicicola, Alternaria citri, Aspergillus niger and Rhizopus stolonifer in fruits. The findings of this paper have recommended these yeast strains and their toxins as effective biocontrol agents against fungi that cause post-harvest diseases.

A cross-sectional study of variations in the biophysical parameters of skin among healthy volunteers.

BACKGROUND: Biophysical parameters of skin such as trans-epidermal water loss (TEWL), hydration, elasticity, pH, and sebum reflects it functional integrity. Advances in technology have made it possible to measure these parameters by non-invasive methods. These parameters are useful for the prediction of disease and its prognosis. It also helps in developing new skin care products according to various skin types, and to evaluate, modify, or compare the effects of existing products. AIM: The aim of the study was to measure, evaluate, and analyze variations in biophysical parameters at pre-selected skin sites in healthy Indian volunteers, across different age groups and gender. METHODS: The study was conducted among 500 healthy Indian volunteers, between 5 and 70 years of age, in the outpatient department of dermatology at Sir T. Hospital, Bhavnagar. Biophysical parameters such as TEWL, hydration, elasticity, and sebum content was measured on four pre-selected body sites by a Dermalab instrument (Cortex Technology, Denmark). The skin pH was measured with a sensitive pH probe (BEPL 2100). RESULTS: All parameters were higher in males compared to females, except for sebum content, which was equal in both genders. Transepidermal water loss and hydration was lower in middle and older age groups. The skin pH showed no statistically significant difference with age. Sebum content was higher in middle and older age groups. The nose had the highest sebum content across all age groups. The forehead showed higher median values of TEWL and hydration compared to other sites. Though elasticity has highest value on forearm, only leg region showed statistically significant value. LIMITATIONS: The present study was confined to a single geographical area, so the effect of environment changes could not be judged accurately. Seasonal variations were not studied as it was a cross-sectional study. CONCLUSION: Skin properties vary with age, gender, and location on the body. This knowledge will help to create a database of these parameters in the Indian population. It would assist in the diagnosis of various clinical conditions and monitor therapeutic response.

Effect of GAPDH-derived antimicrobial peptides on sensitive yeasts cells: membrane permeability, intracellular pH and H+-influx/-efflux rates.

Saccharomyces cerevisiae secretes antimicrobial peptides (AMPs) derived from glyceraldehyde-3-phosphate dehydrogenase (GAPDH), which induce the death of several non-Saccharomyces yeasts. Previously, we demonstrated that the naturally secreted GAPDH-derived AMPs (i.e. saccharomycin) caused a loss of culturability and decreased the intracellular pH (pHi) of Hanseniaspora guilliermondii cells. In this study, we show that chemically synthesised analogues of saccharomycin also induce a pHi drop and loss of culturability in H. guilliermondii, although to a lesser extent than saccharomycin. To assess the underlying causes of the pHi drop, we evaluated the membrane permeability to H+ cations of H. guilliermondii cells, after being exposed to saccharomycin or its synthetic analogues. Results showed that the H+-efflux decreased by 75.6% and the H+-influx increased by 66.5% in cells exposed to saccharomycin at pH 3.5. Since H+-efflux via H+-ATPase is energy dependent, reduced glucose consumption would decrease ATP production and consequently H+-ATPase activity. However, glucose uptake rates were not affected, suggesting that the AMPs rather than affecting glucose transporters may affect directly the plasma membrane H+-ATPase or increase ATP leakage due to cell membrane disturbance. Thus, our study revealed that both saccharomycin and its synthetic analogues induced cell death of H. guilliermondii by increasing the proton influx and inhibiting the proton efflux.