Nitrogen Source Concentration Research Articles

Growth Optimisation and Kinetic Profiling of Diesel Biodegradation by a Cold-Adapted Microbial Consortium Isolated from Trinity Peninsula, Antarctica.

Simple SummaryDiesel fuel is very crucial for anthropogenic activities in Antarctica and the surges in annual demand mean higher likelihood of spillages from improper handling during transportation, storage and disposal processes. The impacts can be very extensive or well-contained depending on the scale of the spills as well as the terrain involved. Nevertheless, the freezing temperature and prolonged solar irradiance in the south pole greatly hampered the natural attenuation and photovolatilisation of petrogenic hydrocarbons, contributing to their persistency. The most susceptible groups are the soil microorganisms, mosses, seabirds and pinnipeds as they are easily found near the shore where hydrocarbons spillage is very common. Microbial bioremediation is a well-established approach in restoring many hydrocarbons-polluted areas, thus the current study focused on the optimisation and application of locally isolated microbial consortium to simulate the in situ diesel clean-up process in aqueous medium. This study highlights the ability of the selected consortium to degrade diesel almost completely at moderately low temperature, suggesting its potential application in Antarctic settings.Pollution associated with petrogenic hydrocarbons is increasing in Antarctica due to a combination of increasing human activity and the continent’s unforgiving environmental conditions. The current study focuses on the ability of a cold-adapted crude microbial consortium (BS24), isolated from soil on the north-west Antarctic Peninsula, to metabolise diesel fuel as the sole carbon source in a shake-flask setting. Factors expected to influence the efficiency of diesel biodegradation, namely temperature, initial diesel concentration, nitrogen source type and concentration, salinity and pH were studied. Consortium BS24 displayed optimal cell growth and diesel degradation activity at 1.0% NaCl, pH 7.5, 0.5 g/L NH4Cl and 2.0% v/v initial diesel concentration during one-factor-at-a-time (OFAT) analyses. The consortium was psychrotolerant based on the optimum growth temperature of 10‒15 °C. In conventionally optimised media, the highest total petroleum hydrocarbons (TPH) mineralisation was 85% over a 7-day incubation. Further optimisation of conditions predicted through statistical response-surface methodology (RSM) (1.0% NaCl, pH 7.25, 0.75 g/L NH4Cl, 12.5 °C and 1.75% v/v initial diesel concentration) boosted mineralisation to 95% over a 7-day incubation. A Tessier secondary model best described the growth pattern of BS24 in diesel-enriched medium, with maximum specific growth rate, μmax, substrate inhibition constant, Ki and half saturation constant, Ks, being 0.9996 h−1, 1.356% v/v and 1.238% v/v, respectively. The data obtained suggest the potential of microbial consortia such as BS24 in bioremediation applications in low-temperature diesel-polluted soils.

Green synthesis of bioemulsifier and exopolysaccharides by Brevibacillus borstelensis and process parameters optimization using response surface model, genetic algorithm and NSGA

Bioemulsifier and exopolysaccharides are industrially important biomolecules produced by microorganisms using green technology. They have applications in food, biomedical, pharmaceutical and cosmetic industries and hence high yield of both products becomes necessary. The current study showed that Brevibacillus borstelensis has a potential to produce bioemulsifier and exopolysaccharide simultaneously but yield of both products is limited. In this study, CCD-RSM has been used as experimental design to increase concentration of both products. Concentrations of glucose, monosodium glutamate, yeast extract and magnesium sulphate were process variables and concentrations of bioemulsifiers, exopolysaccharides and biomass were responses. 30 experimental runs were performed and the models from CCD were optimized by genetic algorithm and NSGA. The results from modelling and optimization techniques were compared along with validation of models. The predicted values from optimization techniques were better than experimental values. The study concluded that NSGA is most suitable to optimize multiple responses simultaneously when compared to RSM and genetic algorithm. The optimum conditions for production were 22 g/l glucose, 14 g/l monosodium glutamate, 6 g/l yeast extract and 0.6 g/l magnesium sulphate with maximum yield of 6.1, 17.6 and 2.8 g/l bioemulsifier, exopolysaccharide and biomass, respectively. Knowledge of optimum concentrations of carbon and nitrogen source will help to utilize industrial and agricultural wastes for production of both products. They have applications in environmental bioremediation by clearing oil spills. Bioemulsifiers also help in heavy metal removal from hazardous waste. Hence this will result in environmental bioremediation by utilization of wastes by employing products generated from wastes.

Lignocellulolytic bacteria isolated from organic rice field soils for enzyme production using agricultural wastes: Screening, medium optimization, and co-culture

Lignocellulolytic bacteria can degrade agricultural biomass and fungal cell walls. Organic agriculture intensively employs these microbes as biofertilizers and biocontrol agents. This study focused on isolating, screening, identifying, and optimizing enzyme production of the lignocellulolytic bacteria obtained from organic rice field soils for utilizing in organic farming. Here we have shown that the farming periods can alter the bacterial biodiversity in organic rice field soil by providing different nutrients. Paenibacillus polymyxa BTK01 and Bacillus subtilis BTK07, which were isolated from the preharvest soil, exhibited a high activity of mannanase (MNN) and xylanase (XLN). By optimizing the enzyme production, BTK01 and BTK07 were specifically productive in xylanase and mannanase, respectively, because of the induction of substrate-like carbon sources. Varying the type and concentration of nitrogen source revealed that mannanase production positively correlated to bacterial growth of both strains. Throughout the study, we used soybean meal as a nitrogen source with the nitrogen concentration of 0.144% (w/v), BTK01 was productive in xylanase when cultured in the medium comprised of 1.5% (w/v) rice straw (0.905 ± 0.016 U/mL), and BTK07 was efficient in mannanase production when cultured in the medium consisted of 1.0% (w/v) copra meal (0.440 ± 0.000 U/mL). The co-culture of BTK01 and BTK07 using the volume ratio of 1:10 could yield MNN and XLN to be 2.470 ± 0.013 and 0.906 ± 0.015 U/mL, respectively. This result demonstrates that Paenibacillus polymyxa BTK01 and Bacillus subtilis BTK07 can be useful and applicable for organic agriculture as biocontrol agents and biofertilizers.

Optimization of culture conditions for cellulase production in Acanthophysium Sp. KMF001 using response surface methodology

There are differences in the extracellular enzymes produced from species of wood-rotting fungi and their activity due to variation in nutritional conditions such as carbon sources and nitrogen sources, as well as environmental conditions such as incubation temperature and pH. In this study, to determine the methods to promote the secretion of especially cellulase with high activity among the extracellular enzymes of wood-damaging fungi, the optimal nutrient sources and incubation conditions for the production of cellulase with high activity were investigated using response surface methodology based on a broth culture from Acanthophysium sp. KMF001, a novel strain of wood-damaging fungus. The nutrient sources that were optimal for the cellulase production with high activity from Acanthophysium sp. KMF001 were cellulose as a carbon source and tryptone:yeast extract (7:3) as a nitrogen source. The optimal incubation conditions were a temperature of 30 °C and a pH of 6. The optimal concentrations of carbon and nitrogen sources were cellulose at 31.1 g∙L-1 and tryptone:yeast extract (7:3) at 15 g∙L-1, with pH of 5.9.

INVESTIGATION OF FERMENTATION CONDITION FOR PRODUCTION ENHANCEMENT OF POLYHYDROXYALKANOATE FROM CHEESE WHEY BY PSEUDOMONAS SP.

A newly acquired polyhydroxyalkanoate (PHA) producing Pseudomonas sp. was characterized based on 16S rRNA gene sequences (1,423 bp) and identified as P. Putida SS9. This strain P. putida SS9 was considered in respect of its potential for achieving maximum production of PHA under controlled volumetric oxygen transfer coefficient (kLa) using inexpensive substrate, cheese whey. The significant parameters such as pH, temperature, nitrogen source concentration were studied in shake flask. The influence of aeration and agitation on kLa and production of PHA was studied in stirred tank fermenter. Maximum PHA concentration of 5.98 and 4.33 g/l was obtained using cheese whey medium (CWM) and mineral salts medium (MSM) respectively. Further, the properties of PHA were analyzed by Differential scanning calorimetry, Thermal gravimetry analysis. The structure of the compound was elucidated by Fourier transform infrared and Nuclear magnetic resonance spectroscopy. The findings suggested that the cheese whey could be a most excellent alternative carbon source for PHA production using P. putida SS9 and thus it could effectively replace the synthetic mineral salts medium under optimum kLa. The nucleotide sequence proclaimed in this work will emerge in the GenBank nucleotide sequence database under accession number MF403057.

Pemanfaatan sumber nitrogen organik dalam pembuatan nata de coco

Nata de coco is made from raw coconut water which is fermented using the Acetobacter xylinum bacteria. This product has the characteristics of a white color, a thickness of approximately 1-2 cm and a chewy texture like a gel. The largest content in nata de coco is fiber known as bacterial cellulose. In addition to requiring sugar as a carbon source, making nata de coco also requires a source of nitrogen to activate the extracellular enzymes of the Acetobacter xylinum bacteria in the manufacture of nata cellulose. Sources of nitogen used in the manufacture of nata de coco generally use inorganic nitrogen sources, which in their development have caused many pros and cons, especially with regard to food safety issues when this product is consumed as a beverage. This study aims to obtain the best alternative nitrogen source and concentration in making nata de coco. The experimental design used in this study was nested randomized design with 2 factors as the first factor, the type of nitrogen source, while the second factor was the concentration of the nitrogen source in the first factor. The types of nitrogen sources used as the first factor were tofu industrial wastewater, green bean sprouts and Azolla microphylla, while the second factor was the concentration of nitrogen sources consisting of 4 levels, namely 0.5%, 1%, 1.5% and 2%. The parameters observed in this study were thickness of nata de coco, weight of nata de coco, crude fiber of nata de coco, number of Acetobacter xylinum cells in the nata de coco layer. The results showed that organic nitrogen sources (tofu, sprouts and Azolla microphylla liquid waste can be an alternative substitute for inorganic nitrogen sources (urea, ZA and ammonium sulfate) which have been commonly used in making nata. The highest quality nata de coco is produced from the treatment of organic nitrogen sources. sprouts with a concentration of 1.5% with a thickness of 2.83 cm, a weight of 279.33 grams, a crude fiber content of 4.14% and the number of Acetobacter xylinum cells in the cellulose layer 0.4 x 107 cells / ml.

Artificial Intelligence as a Combinatorial Optimization Strategy for Cellulase Production by Trichoderma stromaticum AM7 Using Peach-Palm Waste Under Solid-State Fermentation

The use of agro-industrial waste as substrate to produce enzymes has been widely studied in order to adjust the high productions of these biocatalysts with a reduction of the final cost in an ecologically correct process in the industry. This is the first work to use peach-palm (Bactris gasipaes Kunth.) waste for the production of carboxymethylcellulases (CMCase) by the Trichoderma stromaticum AM7 under solid-state fermentation (SSF) using the artificial neural network and genetic algorithm (ANN-GA) to optimize the cellulase production. ANN-AG was used to determine the optimal influence of nitrogen source concentration (2.46%), time (12 days), and temperature (26 °C) on the cellulase production with 98% of efficiency for algorithm prediction of endoglucanase activity. The predicted and experimental values of the CMCase activity in U/g of dry initial substrate (gds) were 122.9 and 120.0, respectively. After all optimization processes, the variation of these parameters allowed a final increase of 31.58-fold when compared to the initial fermentation. Moreover, the treatment of peach-palm waste with T. stromaticum AM7 endoglucanase had an effect on the degradation of the fibers analyzed by scanning electron microscopy and the saccharification of the waste by releasing reducing sugar (807.80 mg/g) for 8 h of incubation. These results are very promising to waste valorization and the biotechnological and industrial applications of cellulase of the T. stromaticum AM7 to food processes and biofuel production.

Statistical optimization of L-asparaginase production by Cladosporium tenuissimum

Background L-asparaginase produced by plant and bacteria can be used in the pharmaceutical and food industry. Unlike the bacterial counterparts, fungal L-asparaginase has more stability, more activity, and less adverse effects. Central composite design (CCD) was used to optimize temperature, pH, incubation time, and carbon-to-nitrogen ratio for L-asparaginase production by Cladosporium tenuissimum via submerged fermentation. CCD reduces the number of tests and time for optimization. Objective To optimize the culture conditions, such as temperature, pH, production time, and the ratio between concentration of carbon and nitrogen sources, for the production of L-asparaginase by isolated C. tenuissimum via submerged fermentation. Materials and methods Primarily, four significant parameters (temperature, pH, incubation period, and carbon-to-nitrogen ratio) were identified that affect the production process of L-asparaginase via submerged fermentation using the modified Czapek Dox medium. CCD was used to optimize the selected parameters concurrently, and their results were compared. Results and conclusions The highest L-asparaginase enzyme activity obtained was 2.6471 U/ml at 37°C, pH 6.2, incubation time 72 h, and 2 : 1 carbon-to-nitrogen ratio. The P value of interaction between every two factors was only significant for the interaction between temperature and incubation period (P

Adverse effects of nitrogenous compounds on nitrogen-fixing cyanobacterium Anabaena solitaria Klebahn

The nitrogen-fixing heterocystous cyanobacterium Anabaena solitaria was tested for its response to different concentrations of nitrogen sources, namely nitrate and ammonia. To compare both the effect of concentration and type of nitrogen source, gradual concentrations were prepared for both ammonia and nitrate. The results showed concentration was significantly important on the frequency of heterocyst formation where highest nitrogen compounds concentrations were inhibitory for heterocyst formation. On the other hand, the effect of the type of nitrogenous compounds tested was insignificant which only proves that they are equally usable by cyanobacteria which will use them instead of transforming one of its cells to heterocyst thus not performing nitrogen fixation. Results also revealed the massive growth of heterotrophic bacteria in presence of nitrogenous compounds. This indicates that the presence of nitrogenous compounds in fields in which nitrogen-fixing cyanobacteria are to be used as biofertilizers can be inhibitory for nitrogen fixation and stimulatory for heterotrophic bacterial growth which could be pathogenic and harmful to plants. The use of more nitrogen-fixing cyanobacteria with the minimum amount of nitrogenous compounds is recommended.

The preliminary optimization of culture components for improving antifungal production by a wild-type soil bacteria Bacillus subtilis

Antifungal compounds are produced by Bacillus species under various growth conditions. While optimizing the antifungal production by using the one-factor-at-a-time (OFAT) and response surface methodology (RSM) approaches mannose and malt extract were identified as the most suitable carbon and nitrogen sources respectively. The RSM was applied to determine the optimum conditions of the three parameters such as pH, carbon and nitrogen sources for improved production. Optimum concentrations of carbon and nitrogen sources were 0.3% and 0.6% respectively with optimum media pH of 7.0 which showed optimum value of 40 AU/ml of antifungal compound against the Candida albicans SC5314 used as an indicator strain. In the present study, the F-value was determined as 0.0034 to imply that the model is significant. The goodness of the fit of the model was tested using coefficient of determination, R2 value, that tantamounts to 0.8562. The identification of antifungal compounds with their molecular masses was accomplished by MALDI-TOF mass spectrometry after n- butanol extraction. The present study thus has provided a platform to upgrade the yield of antifungal compounds which have got immense clinical potential to tread Candidosis.

Effect of Type of Nitrogen Sources and Concentration on Protease Production: Fish Waste Hydrolysate as a Potential Low Cost Source

Fish waste hydrolysate is obtained from hydrolysis process of a fishery industry waste. It can be a good substrate source for the production of protease via a fermentation process. Protease covers above than 50% of the global industrial enzymes market and is regarded as an enzyme which is widely used in many applications. This research aims to determine the effect of the type of nitrogen sources and nitrogen source concentration on protease production from the fish waste hydrolysate. The experiments were done using one factor at a time (OFAT) of type of nitrogen sources and nitrogen source concentration in submerged fermentation (SmF) of 10% (v/v) Bacillus cereus (ATCC 10876). In the first stage, the variation of type of 1% (w/v) nitrogen sources such as fish waste hydrolysate, beef extracts, yeast extracts, tryptone, peptone and skim milk powder that mixed with the basal media were compared to evaluate the highest protease production. Then, the concentration of fish waste hydrolysate was varied from 1% to 3% (w/v) to analyse the production trend of protease. The protease activity and total protein content were then analysed by protease assay using tyrosine as a standard and Bradford method, respectively. Upon the observation, 1% (w/v) nitrogen sources on protease production revealed that the fish waste hydrolysates and beef extracts were capable to produce a high amount of protease (23.659 ± 0.38 U/mL and 28.7631 ± 0.59 U/mL, respectively). Among the concentration tested, 3% (w/v) of fish waste hydrolysate was found to be the highest protease production (190.85 ± 0.38 U/mL). Therefore, the fish waste hydrolysate has a potential as a low-cost source for protease production.

Nutrient removal by Arthrospira platensis cyanobacteria in cassava processing wastewater

Industrial processing of cassava and other starch-containing tubercles generates high amounts of nutrient-rich wastewater that cannot be directly disposed in rivers or lakes. This work evaluates the bioremediation of cassava processing wastewater using the cyanobacteria Arthrospira platensis, focusing on removing nitrogen and phosphorous sources. An experimental design was carried out comprising treatments consisting in the feed of 0.0–2.0 mL/day of cassava processing wastewater per liter of culture in a feed-batch operation. The experiments were carried out at pH 11.0 and 23 °C. The effects of cassava processing wastewater were evaluated on the number of trichomes, growth rate, number of divisions per day, generation time, and nutrient consumption by the cyanobacteria. Arthrospira platensis bioremediation had improved performance at 1.5 mLwastewater/day/Lculture of cassava processing wastewater regarding the growth of colonies and removing nutrients from the wastewater. The treatment at low feed rates resulted in total removal of ammonia and nitrites, and partial removal of nitrates and phosphates. The result indicates that Arthrospira platensis could be applied in bioremediation of agroindustry wastewaters that contain high concentrations of nitrogen sources, especially ammonia and nitrites. However, industrial treatment should be carried out in stabilization ponds due to the low required feed rate for optimal removal of nutrients.

Usage potential of apple and carrot pomaces as raw materials for newly isolated yeast lipid-based biodiesel production

It is vital to determine the novel oleaginous yeasts for biodiesel production, and lignocellulosic by-products have various advantages as growth media for microbial lipid production. By this context, in this study, lipid accumulation capacities and biodiesel production potentials of two newly isolated yeasts (Candida albicans and Kluyveromyces marxianus) were investigated. Sustainable agricultural wastes such as carrot and apple pomaces were used for lipid accumulation experiments. Some critical parameters such as pH (3–6), initial pomace loading (6%–12%), nitrogen type (soy wheat, urea, whey, KNO3, NH4NO3, and NH4Cl), and concentration (0.25–1.5 g/L) of nitrogen sources, incubation time (24–96 h), and solvent type in lipid extraction (n-hexane, chloroform:methanol, chloroform, methanol, and ethanol) were optimized. The maximum lipid concentrations and total C16 + C18 fatty acid methyl ester yields were found as 41.3% and 74.1% for C. albicans and 37.8% and 84.6% for K. marxianus, respectively. Because of some critical fuel properties of the fatty acid methyl esters such as cetane number, kinematic viscosity, and iodine value that were matched well with ASTM D6751 and EN 14214 standards, this study shows that apple and carrot pomaces are promising feedstocks for yeast lipid-based biodiesel production.

Production of Soybean Plants for Hydroponic Cultivation from Seedling Cuttings in a Medium Containing Rhizobium Inoculum Depending on Various Concentrations of Nutrient Solution and Different Nitrogen Sources

Abstract There has been an increasing interest in soybean cultivation in hydroponic systems. Because soybean plants can utilize nitrogen derived from biological N2 fixation, the use of Rhizobium inoculated plants may eliminate or decrease the need for mineral nitrogen fertilization in hydroponic systems. Thus, the objective of this study was to establish effective methods for making inoculated soybean transplants for a substrate-based hydroponic system. Inoculated plants were effectively produced by rooting seedling stem cuttings in a medium containing a Rhizobium inoculant. We also investigated the effects of different nitrogen forms and sub-irrigated nutrient solution concentrations on the growth and root nodule formation of the inoculated plants. The application of a nitrogen-free nutrient solution had minimal positive effects on the growth and nodulation of the inoculated plants. Ammonium-fed plants lacked root nodules regardless of the ammonium concentration. Furthermore, a 50% nutrient solution combining with nitrate or urea as the nitrogen source did not promote root nodulation. Therefore, inoculated plants should be subirrigated with an approximately 25% nutrient solution supplemented with nitrate or urea to induce early growth and nodulation prior to transplantation.

Bioaccumulation of fluoride from aqueous system and genotoxicity study on Allium cepa using Bacillus licheniformis

Removal of fluoride (F‐) was performed using a novel bacterium isolated from F- contaminated soil collected from Pappireddipatti block of Dharmapuri District in Tamil Nadu, India. Impact of changing variables for the removal of F- from synthetic medium at different concentrations of carbon and nitrogen sources (0.5, 1.0 and 1.5 g) was studied with bio inoculants of the bacterial strain (PPR8). The effects of different environmental parameters viz., pH (5.0–9.0) and temperature (25−45 °C) on the biosorption of F- biosorption were also evaluated. The strain PPR8 was identified as Bacillus licheniformis through 16S rRNA sequencing and phylogenetic analysis. Bioaccumulation of F- in the bacterial cells was confirmed by FTIR, SEM and TEM-EDAX and almost 97% of F- removal was established. To test the potential applicability of the bacterium, the bioreactor study was carried out with F- contaminated groundwater collected from the contaminated area. Furthermore, the treated and untreated F- contaminated waters were used to evaluate the genotoxicity on the root cells of onion (Allium cepa) by root tip assay. The experimental results proved that the significant removal of F- by Bacillus licheniformis PPR8 (KX646393) and it could be used as a potential adsorbent in removing F- from contaminated ground waters.

Improvement of carotenoids production from Rhodotorula glutinis CCT-2186

Abstract Rhodotorula strains can produce industrial valuable bioproducts. In this work, the production of carotenoids, and lipids by Rhodotorula glutinis using different nitrogen sources was evaluated. Two statistical experimental designs were applied to improve carotenoid production: a first 25−1 fractional factorial design evaluating the influence of independent variables pH, nitrogen source, glucose, KH2PO4 and MgSO4 concentration; a second 22 central factorial design to optimize the effect of pH and nitrogen sources. After the optimization using two statistical designs, a culture mediium composed of (in g/L) glucose (10), asparagine (10), NH4NO3 (4), KH2PO4 (0.52), MgSO4 (0.52) was found as the best for the production of carotenoids at a pH 5 and 30 °C. The best bioprocess was scaled-up to a 5 L stirred-tank bioreactor. The change to a bioreactor allowed to improve aeration and agitation conditions, and consequently, increasing the production yields (m/v) in, approximately, 25.83 %, 11.88 %, 24.50 % and 10.32 % for β-carotene, torularhodin, torulene and lipids, respectively. The combined supplementation of the culture media with both organic (asparagine) and inorganic nitrogen (ammonium nitrate) sources was primordial for enhancing the carotenogenesis. R. glutinis are very efficient in the production of valuable carotenoids and lipids, presenting high potential of yeast for the industrial production of more sustainable cosmetic, pharmaceutical, and food products.

Bio-designing of Culture Conditions for Chlorella vulgaris Using Response Surface Methodology

Microalgae are microscopic organisms and show a geographical distribution depending on the physical, dynamic, and chemical factors of the environment. These factors are mostly important for attachment and development of microalgae. Substrate, temperature, light, agitation, and turbidity can be given as examples of physical factors, whereas salinity, pH value, and vitamins can be categorized as chemical factors. In this study, the optimization of Chlorella vulgaris production was carried out by response surface methodology (RSM) using two factors of agitation rate (100-250 rpm) and nitrogen source concentration (1-4 g/L) in the cultivation of BG11 medium. Moreover, the usage of urea instead of NaNO3 was investigated and discussed. 

Nitrogen Optimization on Rhamnolipid Biosurfactant Production from Pseudoxanthomonas sp. G3 and Its Preservation Techniques

Biosurfactant is a microbial bioproduct that is used to reduce the surface tension, and can acted as emulsifier, dispersant, and anti-adhesive. Optimization of biosurfactant production needs to be done, not only to increase its production quantity, but also to reduce overall production cost. This study aims to determine the most suitable and optimum concentration of nitrogen source for biosurfactant production and its preservation techniques. The biosurfactant was produced by Pseudoxanthomonas sp. G3 using minimal salt medium with 2% light crude oil as carbon source and different nitrogen sources in the form of urea, sodium nitrate, and ammonium nitrate. The activity of biosurfactants were measured by emulsification index (E24), interfacial tense (IFT), oil drop assay, and dry weight. Potassium sorbate 0.2% (w/v) was used as preservative agent. The results showed that biosurfactant production using sodium nitrate as a nitrogen source provides the highest activity and yield. The E24 value was 76.63% and the clear zone diameter observed was 0.875 cm. The overall decreased in IFT was 35.4% and the biosurfactant dry weight was 0.45 gL-1. Microbial contamination occurred after 3 weeks of storage in the treatment without the addition of preservative. It also showed that the activity of biosurfactants (emulsification and IFT) were gradually decreased during storage. In conclusion, the optimum biosurfactant production by Pseudoxanthomonas sp. G3 was obtained by the addition of sodium nitrate 0.3% (w/v). Meanwhile, the most effective biosurfactant preservation method was by adding potassium sorbate which was stored at 4 ℃.

Parametric optimization and kinetic study of l-lactic acid production by homologous batch fermentation of Lactobacillus pentosus cells.

Parametric optimization always plays important roles in bioengineering systems to obtain a high product yield under the proper conditions. The parametric conditions of lactic acid production by homologous batch fermentation of Lactobacillus pentosus cells was optimized by the Box-Behnken design. The highest l-lactic acid yield was obtained as 0.836±0.003 g/g glucose with the productivity of 0.906±0.003g/(L×H) under the optimum conditions of 34.7 °C, pH 6.2, 148 rpm agitation speed, and 9.3g/L nitrogen source concentration determined by quadratic response surface with high accuracy. The adequate kinetic models of cell growth rate, lactic production rate, and glucose consumption rate were also established to describe the fermentation behavior of L. pentosus cells with the correlation coefficients of 09985, 0.9990, and 0.9989, respectively.

A Deuteromycete Isolate Geotrichum candidum as Oleaginous Cell Factory for Medium-Chain Fatty Acid-Rich Oils.

Single cell oils (SCO) are oils derived from microorganisms which have potential to hyperaccumulate intracellular lipids (called oleaginous) under some essential nutrient (nitrogen, phosphorous or sometimes sulphur) starvation and an excess of carbon. The present work investigates the influence of these key parameters (for triggering oleaginicity), i.e. carbon (C) and nitrogen (N) on oleaginous behaviour of an oleaginous isolate, with the objective of improving the lipid content and obtaining oils of applicative interest. Eleven yeasts were isolated from rotten fruits and a unique yeast from rotten apple was screened on the basis of its ~20% (of dry mass) lipid content (LC),trademark of oleaginicity under nitrogen-stressed culture conditions. Subsequent investigation on influence of C, N and w/w ratio of carbon source concentration (Cs) to nitrogen source concentration (Ns) was conducted on this isolate. The isolate was identified as a Deuteromycete-Geotrichum candidum. 4.8g/l was found to be minimum N concentration and glucose as suitable C source for optimum balance between biomass and lipid content. The highest LC of 73.6% (172.5% higher compared to 27% LC at Cs/Ns 80/4.8) was obtained at Cs/Ns 150/4.8 with a lipid coefficient of 8.7 (g lipid/100g substrate). While remarkably higher production economy (lipid coefficient of 28.45) was noted at Cs/Ns 100/4.8 with significant LC of 54.4% (~ 100% higher than at Cs/Ns 80/4.8). The derived oils were predominantly rich in medium-chain fatty acids (MCFA)-caprylic acid, rare in plant oils. G. candidum is a previously referred oleaginous species; however, for the first time this study illustrates its detailed oleaginous behaviour and lipid compositional characteristics with varying nutritional parameters. The work is a progressive contribution towards current and upcoming researches in field of SCOs. Compositional characteristics of derived oils, make it an important candidate for potential medical and nutritional applications in future.