Parul A. Pruthi

Exopolysaccharide analysis of biofilm-forming Candida albicans.

Aim:  The major objective of the study was to analyse exopolysaccharide produced by a biofilm forming‐clinical strain of Candida albicans.

Biodiesel production from non-edible lignocellulosic biomass of Cassia fistula L. fruit pulp using oleaginous yeast Rhodosporidium kratochvilovae HIMPA1

This study explored biodiesel production from a low cost, abundant, non-edible lignocellulosic biomass from aqueous extract of Cassia fistula L. (CAE) fruit pulp. The CAE was utilized as substrate for cultivating novel oleaginous yeast Rhodosporidium kratochvilovae HIMPA1. This oleaginous yeast accumulates high amount of triacylglycerides as large intracellular lipid droplets (4.35±0.54μm) using CAE as sole nutritional source. Total lipids (4.86±0.54g/l) with lipid content of 53.18% (w/w) were produced by R. kratochvilovae HIMPA1 on CAE. The FAME profile obtained revealed palmitic acid (C16:0) 43.06%, stearic acid (C18:0) 28.74%, and oleic acid (C18:1) 17.34% as major fatty acids. High saturated fatty acids content (72.58%) can be blended with high PUFA feedstocks to make it an industrially viable renewable energy product.

Boosting accumulation of neutral lipids in Rhodosporidium kratochvilovae HIMPA1 grown on hemp (Cannabis sativa Linn) seed aqueous extract as feedstock for biodiesel production

Hemp seeds aqueous extract (HSAE) was used as cheap renewable feedstocks to grow novel oleaginous yeast Rhodosporidium kratochvilovae HIMPA1 isolated from Himalayan permafrost soil. The yeast showed boosted triglyceride (TAG) accumulation in the lipid droplets (LDs) which were transesterified to biodiesel. The sonicated HSAE prepared lacked toxic inhibitors and showed enhanced total lipid content and lipid yield 55.56%, 8.39±0.57g/l in comparison to 41.92%, 6.2±0.8g/l from industrially used glucose synthetic medium, respectively. Supersized LDs (5.95±1.02μm) accumulated maximum TAG in sonicated HSAE grown cells were visualized by fluorescent BODIPY (505/515nm) stain. GC-MS analysis revealed unique longer carbon chain FAME profile containing Arachidic acid (C20:0) 5%, Behenic acid (C22:0) 9.7%, Heptacosanoic acid (C27:0) 14.98%, for the first time in this yeast when grown on industrially competent sonicated HSAE, showing more similarity to algal oils.

Synergistic dynamics of nitrogen and phosphorous influences lipid productivity in Chlorella minutissima for biodiesel production.

The study synergistically optimized nitrogen and phosphorous concentrations for attainment of maximum lipid productivity in Chlorella minutissima. Nitrogen and phosphorous limited cells (N(L)P(L)) showed maximum lipid productivity (49.1±0.41mg/L/d), 1.47 folds higher than control. Nitrogen depletion resulted in reduced cell size with large sized lipid droplets encompassing most of the intracellular space while discrete lipid bodies were observed under nitrogen sufficiency. Synergistic N/P starvations showed more prominent effect on photosynthetic pigments as to individual deprivations. Phosphorous deficiency along with N starvation exhibited 17.12% decline in carbohydrate while no change in nitrogen sufficient cells were recorded. The optimum N(L)P(L) concentration showed balance between biomass and lipid by maintaining intermediate cell size, pigments, carbohydrate and proteins. FAME profile showed C14-C18 carbon chains in N(L)P(L) cells with biodiesel properties comparable to plant oil methyl esters. Hence, synergistic N/P limitation was effective for enhancing lipid productivity with reduced consumption of nutrients.

Antibiofilm activity of quercetin- encapsulated cytocompatible nanofibers against Candida albicans

In this study, nanofibers against pro dimorphic fungal sessile growth were developed. Quercetin was successfully encapsulated within poly(d,l-lactide-co-glycolide)–poly(ε-caprolactone) nanofibers using an electrospinning technique. Field emission scanning electron microscopy, fluorescent microscopy, and Fourier-transformed infrared spectrometer were used to confirm the formation as well as encapsulation of quercetin within the nanofibers. These fabricated nanofibers were further evaluated to determine the effectiveness of the antibiofilm activity against Candida albicans. The cytocompatibility of quercetin-encapsulated nanofibers was found to be similar to control and pure polymeric nanofibers based on 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay against human embryonic kidney (HEK-293) cell lines. These fabricated nanofibers potentially could be used as coatings on biomedical devices to inhibit microbial contaminations.

Process optimization for fabrication of gellan based electrospun nanofibers.

In this investigation, the nanofiber formation ability of gellan, a FDA approved low cost natural polysaccharide, has been achieved for the first time using electrospinning technique. The gellan based ultrafine nanofibers were fabricated by using a blend mixture of gellan with another biodegradable polymer polyvinyl alcohol (PVA). The morphology of resulting gellan-PVA nanofibers was analyzed using field emission scanning electron microscopy (FESEM). The mass ratio of 50:50 for gellan:PVA was recorded as an optimum solution ratio to obtain uniform bead free nanofibers with an average diameter of 40 ± 15.8 nm. Data depicted that among different parameters evaluated, viscosity and the mass ratio of gellan:PVA were the key parameters that influence the nanofiber morphology and diameter.

A novel gellan-PVA nanofibrous scaffold for skin tissue regeneration: Fabrication and characterization.

In this investigation, we have introduced novel electrospun gellan based nanofibers as a hydrophilic scaffolding material for skin tissue regeneration. These nanofibers were fabricated using a blend mixture of gellan with polyvinyl alcohol (PVA). PVA reduced the repulsive force of resulting solution and lead to formation of uniform fibers with improved nanostructure. Field emission scanning electron microscopy (FESEM) confirmed the average diameter of nanofibers down to 50 nm. The infrared spectra (IR), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analysis evaluated the crosslinking, thermal stability and highly crystalline nature of gellan-PVA nanofibers, respectively. Furthermore, the cell culture studies using human dermal fibroblast (3T3L1) cells established that these gellan based nanofibrous scaffold could induce improved cell adhesion and enhanced cell growth than conventionally proposed gellan based hydrogels and dry films. Importantly, the nanofibrous scaffold are biodegradable and could be potentially used as a temporary substrate/or biomedical graft to induce skin tissue regeneration.

Synergistic effect of fermentable and non-fermentable carbon sources enhances TAG accumulation in oleaginous yeast Rhodosporidium kratochvilovae HIMPA1

Novel strategy for enhancing TAG accumulation by simultaneous utilization of fermentable and non-fermentable carbon sources as substrate for cultivation of oleaginous yeast Rhodosporidium kratochvilovae HIMPA1 were undertaken in this investigation. The yeast strain showed direct correlation between the size of lipid bodies, visualized by BODIPY stain (493-515 nm) and TAG accumulation when examined on individual fermenting and non-fermenting carbon sources and their mixtures. Maximum TAG accumulation (μm) in glucose (2.38 ± 0.52), fructose (4.03 ± 0.38), sucrose (4.24 ± 0.45), glycerol (4.35 ± 0.54), xylulose (3.94 ± 0.12), and arabinose (2.98 ± 0.43) were observed. Synergistic effect of the above carbon sources (fermentable and non-fermentable) in equimolar concentration revealed maximum lipid droplet size of 5.35 ± 0.76 μm and cell size of 6.89 ± 0.97 μm. Total lipid content observed in mixed carbon sources was 9.26 g/l compared to glucose (6.2g/l). FAME profile revealed enhanced longer chain (C14:0-C24:0) fatty acids in mix carbon sources.

Drug functionalized microbial polysaccharide based nanofibers as transdermal substitute

In order to promote the natural healing process, drug-functionalized nanofibrous transdermal substitute was fabricated using gellan as chief polymer and polyvinyl alcohol (PVA) as supporting polymer via electrospinning technique. These fabricated nanofibers physiochemically mimic the extracellular matrix (ECM) which supports the cell growth. For neo-tissue regeneration in a sterilized environment, amoxicillin (Amx) was entrapped within these nanofibers. Entrapment of Amx in the nanofibers was confirmed by FESEM, FTIR, XRD and TG analysis. In vitro cell culture studies revealed that the fabricated non-cytotoxic nanofibers promoted enhance cell adherence and proliferation of human keratinocytes. A preliminary in vivo study performed on rat model for full thickness skin excision wound demonstrated the prompt re-epithelialization in early phase and quicker collagen deposition in later phases of wound healing in case of Amx-functionalized gellan/PVA nanofibers. Data collectively confirmed the potential usage of gellan based electrospun nanofibers as transdermal substitute for faster skin restoration.

Structural Characterization and Antimicrobial Activity of a Biosurfactant Obtained From Bacillus pumilus DSVP18 Grown on Potato Peels.

Background: Biosurfactants constitute a structurally diverse group of surface-active compounds derived from microorganisms. They are widely used industrially in various industrial applications such as pharmaceutical and environmental sectors. Major limiting factor in biosurfactant production is their production cost. Objectives: The aim of this study was to investigate biosurfactant production under laboratory conditions with potato peels as the sole source of carbon source. Materials and Methods: A biosurfactant-producing bacterial strain (Bacillus pumilus DSVP18, NCBI GenBank accession no. GQ865643) was isolated from motor oil contaminated soil samples. Biochemical characteristics of the purified biosurfactant were determined and its chemical structure was analyzed. Stability studies were performed and biological activity of the biosurfactant was also evaluated. Results: The strain, when grown on modified minimal salt media supplemented with 2% potato peels as the sole carbon source, showed the ability to reduce Surface Tension (ST) value of the medium from 72 to 28.7 mN/m. The isolated biosurfactant (3.2 ± 0.32 g/L) was stable over a wide range of temperatures (20 - 120 ºC), pH (2-12) and salt concentrations (2 - 12%). When characterized using high-performance liquid chromatography (HPLC) and Fourier transform infrared spectroscopy, it was found to be a lipopeptide in nature, which was further confirmed by Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (mass peak 1044.60) and nuclear magnetic resonance (NMR) studies. Data showed that the isolated biosurfactant at the concentration range of 30 - 35 µg/ml had strong antimicrobial activity when tested against standard strains of Bacillus cereus, Escherichia coli, Salmonella enteritidis, Staphylococcus aureus and Paenibacillus larvae. Conclusions: Potato peels were proved to be potentially useful substrates for biosurfactant production by B. pumilus DSVP18. The strain possessed a unique property to reduce surface tension of the media from 72 to 28.7 mN/m. In addition, it showed a stable surface activity over a wide range of temperatures, pH, and saline conditions and had strong antimicrobial activity. This potential of the identified biosurfactant can be exploited by pharmaceutical industries for its commercial usage.