Mineral Salt Solution Research Articles

Production of a xylanolytic enzyme by a thermoalkaliphilic Bacillus sp. JB-99 in solid state fermentation

Bacillus sp. JB-99 was studied for the production of extra-cellular thermostable alkaline cellulase-free xylanase in solid-state fermentation. The xylanase tit was highest on rice bran, among a few easily available lignocellulosic solid substrates tested. Maximum production of xylanase (3644 U/g DBB) was observed bran moistened with mineral salt solution (MSS 3) at a substrate-to-moisturizing agent ratio of 1:2.0 (w/v) at 50 °C for 72 h. A 10% (v/w) inoculum was most suitable to attain a high production of xylanase. Yeast extract, beef extract and xylan enhanced enzyme production, while glucose, lactose and fructose strongly repressed the production process.

Erosion resistance of 40Kh steel after mechanical-pulse treatment

The mechanical-pulse treatment of 40Kh steel by means of frictional contact of the working surface with a special tool in different technological media enhances the resistance of steel to cavitation- erosion fracture. Mechanical-pulse treatment in a technological medium based on aqueous solutions of calcium and magnesium mineral salts enhances the resistance of 40Kh steel to cavitation- erosion fracture over the entire range of cavitation intensities under study.

Rennin‐like milk coagulant enzyme produced by a local isolate of Mucor

Among 20 isolates of Mucor isolated from various environments in Jordan and found to produce a rennin‐like acid protease, known as Mucor rennin‐like enzyme (MRE), Mucor J20 was found to produce the highest level of MRE. The optimum incubation conditions for enzyme production in a fortified wheat bran mixture using solid‐state fermentation were 3–4 days at 30°C. The highest MRE activity (185–200 rennin units or RU) was produced in a medium containing wheat bran and lentil straw (1 : 1 w/w) moistened with whey, and incubated in clay pots at 30°C for 4 days. A slightly lower activity value (178 RU) was found when using a mineral salt solution or distilled water instead of whey, or when using wheat bran alone with whey. At pH 4, the MRE retained its complete activity (100%) for 6 weeks at 5°C and 10°C, and for 3 and 2 weeks at 20°C and 30°C, respectively. After heating at 60°C for 10 min, the enzyme lost its activity at all pH levels used (pH 2–8). The crude extract of MRE was successfully applied in the manufacture of a cheese curd.

Investigations on neomycin production with immobilized cells of Streptomyces marinensis NUV-5 in calcium alginate matrix.

The purpose of this investigation was to study the effect of Streptomyces marinensis NUV-5 cells immobilized in calcium alginate for the production of neomycin. The effect of various parameters, such as the effect of alginate concentration (1%, 2%, 3%, 4%, and 5% wt/vol), the effect of cation (CaCl2, BaCl2, and SrCl2), the concentration of cation (0.01M, 0.125M, 0.25M, 0.375M, and 0.5M), the curing times (1, 6, 11, 16, and 21 hours), and the diameter of the bead (1.48, 2.16, 3.24, 4.46, and 5.44 mm), on neomycin production and bead stability were studied. The effect of maltose (4%, 3%, 2%, and 1% wt/vol) and sodium glutamate (0.6%, 0.3%, 0.15%, and 0.075% wt/vol) concentration on neomycin production was also studied. Better neomycin production was achieved with optimized parameters, such as alginate at 2% wt/vol, 0.25M CaCl2, 1-hour curing time, and 3.24 mm bead diameter. Effective neomycin production was achieved with 3% wt/vol maltose and 0.6% wt/vol sodium glutamate concentration. The repeated batch fermentations were conducted (every 96 hours) using the optimized alginate beads, employing the production medium with 3% wt/vol maltose and 0.6% wt/vol sodium glutamate along with mineral salts solution. The increase in antibiotic production was observed up to the 5th cycle, and later gradual decrease in antibiotic production was observed. Comparison of the total antibiotic production with free cells and immobilized cells was also done. An enhanced antibiotic productivity of 32% was achieved with immobilized cells over the conventional free-cell fermentation, while 108% more productivity was achieved over the washed free-cell fermentation. From these results it is concluded that the immobilized cells of S marinensis NUV-5 in calcium alginate are more efficient for the production of neomycin with repeated batch fermentation.

Response surface methodological approach to optimize the nutritional parameters for neomycin production by Streptomyces marinensis under solid-state fermentation

The effect of supplementary nutrients on neomycin production was studied using Streptomyces marinensis NUV-5 in solid-state fermentation. Dextrin, raspberry seed powder, and concentrated mineral medium produced high neomycin yields and were selected for optimization. A full factorial composite experimental design and response surface methodology were used in the design of experiments and in the analysis of results. The maximum productivity of antibiotic under optimum conditions was 17 150 mg kg −1 of wheat rawa. The optimum conditions were dextrin 14.1 g kg −1 rawa, raspberry seed powder 64.91 g kg −1 rawa, and mineral salt solution 172.6 ml kg −1 rawa. This method was efficient; only 20 experiments were necessary to assess these conditions and model adequacy was very satisfactory, as the coefficient of determination was 0.9560.

Production of xylanase by Emericella nidulans NK-62 on low-value lignocellulosic substrates

Thermotolerant Emericella nidulans NK-62 was isolated from bird nesting material and was tested for its ability to produce xylanase. The fungus when grown on a medium containing wheat bran (2% w/v) supplemented with Czapek's mineral salt solution at 45 °C for 7 days produced 362 IU/ml of xylanase (EC 3.2.1.8). The specific activity of E. nidulans NK-62 xylanase was found to be 275 IU/mg of total protein. The enzyme was found to be active over a broad temperature and pH range with 60 °C as optimum temperature for enzyme activity. The enzyme was stable at 50 °C and its half-life at 55 °C was 45 min. β-xylosidase (EC 3.2.1.37) and carboxymethylcellulase (EC 3.2.1.4) activities, 0.018 and 0.21 IU/ml respectively, were also noticed. The fungus was screened for its ability to produce xylanase on four different lignocellulosic substrates. It produced 318.9 IU/ml of cellulase-free xylanase on corn cobs. The fungus could also utilize lentil bran (seed husk of Lens esculentus) and meal of groundnut shells to produce 84.8 and 17.3 IU/ml xylanase respectively.

Biofiltration of volatile ethanol using sugar cane bagasse inoculated with Candida utilis

Candida utilis ( C. utilis) growing on sugar cane bagasse complemented with a mineral salt solution was studied for gaseous ethanol removal in a biofilter. Ethanol loads from 93.7 to 511.9 g/h m 3 were used, by varying both inlet ethanol concentration (9.72 to 52.4 g/m 3) and air flow rate (1.59×10 −3 to 2.86×10 −3 m 3/h). At a loading rate of 93.7 g/h m 3, a steady-state was maintained for 300 h. Ethanol removal was complete, and 76.3% of the carbon consumed was found in carbon dioxide. At an higher aeration rate (ethanol load=153.8 g/h m 3), the biofilter displayed an average removal efficiency (RE) of 70%, and an elimination capacity (EC) of 107.7 g/h m 3. Only 64.4% of the carbon consumed was used for CO 2 production. Acetaldehyde and ethyl acetate in the outlet gas attained 7.86 and 20.4% in terms of carbon balance, respectively. In both cases, the transient phase was less than one day. At a high inlet ethanol concentration (52.4 g/m 3), no steady-state was observed and the process stopped during the third day. In the three cases, final biomass was poor, ranging from 10.5 to 14.8 mg/g dm. Final pH 4.0–4.6, indicated that acidifying non-volatile metabolites, such as acetate, accumulated in the reactor.

Toluene mineralization and growth potential of Pseudomonas putida PaW164 under toluene-limiting conditions.

Toluene-induced cells of Pseudomonas putida PaW164 (pWWO-164) were monitored for growth potential, maintaining the TOL plasmid, and potential toluene mineralization activity in toluene-amended and nonamended soil. A follow-up study was done in a carbon-free mineral salts solution to obtain further information on physiological changes that occur during starvation. These studies showed that there was a larger decline in colony forming units (CFUs) recovered on a toluate- or benzoate-defined mineral salts medium than on a complex agar medium, a greater percent decrease of CFU than of potential mineralization activity, no decrease in direct counts, and no loss of the TOL plasmid during starvation. Toluene-induced cells also showed an increasing lag time and a decreasing potential for mineralization of (14)C-toluene with starvation. In contrast, the lag time for mineralization of glucose was longest at the onset of starvation and reached a minimum by 3 days; thereafter, the potential for glucose mineralization remained high.

Investigation of Fe, Mn oxides and organic material in surface coatings and Pb, Cd adsorption to surface coatings developed in different natural waters

Surface coatings (biofilms and associated minerals) were developed on glass slides in five natural waters in Jilin Province, PR China and were used to evaluate Pb and Cd adsorption after they were analyzed for their iron, manganese oxides and organic material content. Pb and Cd adsorption to the surface coatings was measured under controlled laboratory conditions (mineral salt solution with defined speciation, ionic strength 0.05 mol/l, 25°C and pH 6.0). The classical Langmuir and Freundlich adsorption isotherms were applied to estimate equilibrium coefficients of Pb and Cd adsorption to the surface coatings. The results show that the former is more suitable than the latter as a model to describe Pb and Cd adsorption to natural surface coatings. Correlation analyses between the maximum adsorption of Pb and Cd and components in the surface coatings indicate that the adsorption of Pb to Mn oxides and the adsorption of Cd to Fe oxides are statistically higher than the adsorption of Pb and Cd to other components. Moreover, the adsorption of Pb and Cd to organic material is insignificant, highlighting the relative importance of the metal oxide fraction for Pb and Cd adsorption to the surface coatings developed in five natural waters.

Assessing the utility of some technological trains for water recovery from acid and metal salt solutions

Abstract Studies on high-quality water recovery from mineral acid (HCl, H2SO4, HNO3/HF) and iron salt solutions were presented. Water was recovered via three treatment trains involving electrodialysis (ED) and cation exchange in various combinations: System 1: ED1+ED2; System 2: ED1+cation exchange+ED2; and System 3: cation exchange+ED1+ED2. Water recovered via System 3 displayed the highest quality: its conductivity varied from 2 μS/cm (recovery from HCl solution) to 49 μS/cm (recovery from H2SO4 solution). It was found, however, that pre-decationization raised the deionized water consumption for the rinsing of the ion exchanger, thus decreasing the efficiency of water recovery as compared to System 1 or System 2. That is why, the cost of water recovery via System 3 is relatively high. Water can be also recovered via System 1 or System 2. System 2 provided water of slightly better parameters: water contained trace amount of iron salt and its conductivity varied from 4 μS/cm (water from HCl solution) to 61 μS/cm (water from H2SO4 solution). The calculated cost of water production via System 2 is almost the same as that in System 1.

Biogenic production of cyanide and its application to gold recovery.

Chromobacterium violaceum is a cyanogenic (cyanide-producing) microorganism. Cyanide is used on an industrial scale to complex and recover gold from ores or concentrates of ores bearing the precious metal. A potentially useful approach in gold mining operations could be to produce cyanide biologically in relatively small quantities at the ore surface. In this study, C. violaceum grown in nutrient broth formed a biofilm and could complex and solubilize 100% of the gold on glass test slides within 4-7 days. Approximately 50% of the cyanide- recoverable gold could be mobilized from a biooxidized sulfidic-ore concentrate. Complexation of cyanide in solution by gold appeared to have a beneficial effect on cell growth--viable cell counts were nearly two orders of magnitude greater in the presence of gold-coated slides or biooxidized ore substrates than in their absence. C. violaceum was cyanogenic when grown in alternative feedstocks. When grown in a mineral salt solution supplemented with 13.3% v/v swine fecal material (SFM), cells exhibited pigmentation and suspended cell concentrations comparable to cultures grown in nutrient broth. Glycine supplements stimulated production of cyanide in 13.3% v/v SFM. In contrast, glycine was inhibitory when added at the time of inoculation in the more concentrated SFM, decreasing cell numbers and reducing ultimate bulk-solution cyanide concentrations. However, aeration and addition of glycine to stationary phase cells grown on 13.3% v/v SFM anaerobically resulted in rapid production and high concentrations (up to 38 mg l(-1)) of cyanide. This indicates that biogenesis of cyanide may be supported in remote areas using locally produced and inexpensive agricultural feedstocks in place of commercial media.

Adsorption of Pb and Cd onto metal oxides and organic material in natural surface coatings as determined by selective extractions: new evidence for the importance of Mn and Fe oxides

Surface coatings (biofilms and associated minerals) were collected on glass slides in the oxic surface waters of Cayuga Lake (New York State, U.S.A.) and were used to evaluate the relative contributions of Fe, Mn and Al oxides and organic material to total observed Pb and Cd adsorption by the surface coating materials. Several alternative selective extraction techniques were evaluated with respect to both selectivity and alteration of the residual unextracted material. Pb and Cd adsorption was measured under controlled laboratory conditions (mineral salts solution with defined metal speciation, ionic strength 0.05 M, 25°C and pH 6.0) before and after extractions to determine by difference the adsorptive properties of the extracted component(s). Hydroxylamine hydrochloride (0.01 M NH 2OH·HCl+0.01 M HNO 3) was used to selectively remove Mn oxides, sodium dithionite (0.3 M Na 2S 2O 4) was used to remove Mn and Fe oxides, and 10% oxalic acid was used to remove metal oxides and organic materials. Several other extractants were evaluated, but preliminary experiments indicated that they were not suitable for these experiments because of undesirable alterations of the residual, unextracted material. The selected extraction methods removed target components with efficiencies between 71 and 83%, but significant amounts of metal oxides and organic materials other than the target components were also removed by the extractants (up to 39%). Nonlinear regression analysis of the observed Pb and Cd adsorption based on the assumption of additive Langmuir adsorption isotherms was used to estimate the relative contributions of each surface coating constituent to total Pb and Cd binding of the biofilms. Adsorption of Cd to the lake biofilms was dominated by Fe oxides, with lesser roles attributed to adsorption by Mn and Al oxides and organic material. Adsorption of Pb was dominated by Mn oxides, with lesser roles indicated for adsorption to Fe oxides and organic material, and the estimated contribution of Al oxides to Pb adsorption was insignificant. The fitted Pb adsorption isotherm for Fe oxides was in excellent agreement with those obtained through direct experiments and reported in independent investigations. The estimated Pb distribution between surface coating components also agreed well with that previously predicted by an additive adsorption model based on Pb adsorption isotherms for laboratory surrogates for Mn, Fe and Al oxides and defined biological components.

Characterization of volatile compounds produced by Rhizopus strains grown on agro-industrial solid wastes

Four edible Rhizopus strains were cultivated on eight combinations of solid agro-industrial wastes (cassava bagasse, apple pomace), soyabean, amaranth grain and soyabean oil. Significant differences in growth were observed among strains on the different media studied. The medium containing cassava bagasse with soyabean (5:5 w/w) gave the highest CO 2 production, while Rhizopus oryzae ATCC 34612 was the best producer of volatiles. The aromas of the cultures were light and rather pleasant. The amaranth medium with mineral salts solution produced the highest amount of volatile compounds (VC), demonstrating that the aroma of fermented solid substrates can be improved. The VC production was very rapid, attaining, in most of the cases, its maximum around the first day of culture. These maxima markedly varied according to the medium used.

Biodegradation ofs-Triazine Compounds by a Stable Mixed Bacterial Community

The potential for biodegradation ofs-triazine pesticides was investigated in laboratory batch and sequence batch experiments using a stable mixed bacterial community enriched on atrazine. The experiments were performed aerobically in a mineral salt solution complemented with a mixture ofs-triazines as sole carbon and energy sources. Comparisons were made between the efficiency of the inoculum for atrazine degradation in mineral salt solution and in wastewater. In batch cultivation, atrazine, simazine, hydroxyatrazine, and terbutylazine were degraded to concentrations below 0.1 mg/liter after 6 days; evidence of the mineralization was the detection of14CO2from [U-ring-14C] atrazine and the production of nitrate and chloride ions. The low degradation rate observed for cyanuric acid and desethylatrazine suggests that degradation proceeded via N-dealkylation and dechlorination. Nevertheless, degradation of ametryne and cyromazine presume the involvement of other degradation pathways. Evidence was given that presence of other additional carbon sources is not an obstacle to atrazine biodegradation, since better results were obtained using wastewater.

Modulation of metabolic activity prevents degradation of sorbed toluene

The factors affecting the ability of a bacterial species to degrade different amounts of toluene (8.5 to 217 mg/g) sorbed to granular activated carbon (GAC), in an aqueous solution of mineral salts, were investigated. After 144 days the amounts of toluene remaining on one type of GAC ranged from 7.5 to 9.5 mg/g, and the aqueous concentrations of toluene ranged from 2 to 7 μg/L. Neither bacterial death nor an inhibition by accumulating by-products could explain why the remaining toluene had not been degraded. However, at these low concentrations of toluene, and probably because of cell starvation, bacteria were observed to be more than 100-times less efficient to degrade toluene than at high concentrations. We propose that this low degradation ability is responsible for the presence of residual toluene on the GAC, and that this mechanism may contribute to the persistence of low concentrations of sorbed pollutants in the environment.

Dissolution of uraninite in acid solutions

The purpose of this work was to assess the oxidative dissolution of uranium from a uraninite-containing rock in acid sulfate solutions under test conditions relevant to uranium leach mines and acid mine waters. Uranium dissolution in acidified mineral salts solution was slow and the predominant carbonate mineral (rhodochrosite) in the rock sample continued to consume acid. Bacterial inoculation (Thiobacillus ferrooxidans) and additional Fe2+ or S0 were tested in efforts to enhance the dissolution. Addition of Fe enhanced the solubilization of uranium, whereas S-addition had little incremental effect on the dissolution with and without bacterial inoculation. © 1998 Society of Chemical Industry

Isolation of a novel pentachlorophenol-degrading bacterium, Pseudomonas sp. Bu34.

A pentachlorophenol (PCP)-degrading bacterium was isolated from possible PCP-contaminated soil from Pusan, Korea and identified as a member of the genus Pseudomonas. It used PCP as its sole source of carbon and energy. This micro-organism was capable of degrading PCP more effectively, certified by the increase in cell density and the decrease in PCP substrate. Pseudomonas sp. Bu34 was able to degrade a much higher concentration of PCP (4000 mg l-1) than any previously reported PCP-degrading bacteria and fungi and to grow in mineral salts solution containing one of a variety of chlorophenols. In non-acclimated strain Bu34, the cell number decreased from 87 to 99.9% in 75-4000 mg l-1 PCP at 24 h. In the acclimated strain the PCP toxic effect did not appear with 75 mg l-1 PCP treatment, but 1000-4000 mg l-1 PCP decreased the cell number of strain Bu34 by 25% to 24 h and then the cell number slightly increased at 48 h. Therefore, it suggested that the maximum resistance of acclimated strain Bu34 to PCP was 4000 mg l-1 PCP. We suggest that strain Bu34 could be used as a micro-organism for the bioremediation of highly PCP-contaminated soils, water or wood products.

Biodegradation of trichloroethylene by Methylocystis sp. strain M immobilized in gel beads in a fluidized-bed bioreactor

A fluidized-bed bioreactor (FBB) containing Methylocystis sp. strain M (strain M) isolated from Japanese soil was developed for treating synthetic groundwater containing trichloroethylene (TCE). Strain M bacteria were immobilized in 2% calcium alginate gel beads and introduced into the reactor, which was supplied with a methane/air gas mixture. TCE concentrations in the reactor were reduced from 0.9–1.6 to 0.1–0.2 mg/litre after a residence time of 2.56 h. Thus, 80–90% of the influent TCE was degraded in the reactor, and the resulting effluent gas contained only 0.02–0.04 mg/litre TCE. The ability of the gel-immobilized cells to degrade TCE declined rapidly during the TCE degradation process. To compensate for this decrease in activity, the reactor was operated for TCE degradation and reactivation of the immobilized strain M cells on alternate days. TCE degradation activity was completely recovered within 24 h after supplying a methane/air mixture (2:8 v/v) and a mineral salt solution to the bacteria. The degradation capacity of the reactor was kept in a steady state for 10 days in this way, but the rate of recovery of TCE degradation activity gradually decreased. TCE degradation activity fell from 6.0 litres/g dry weight (gdw) per hour on the sixth day to 1.4 litres/gdw per hour on the 24th day. Interestingly, there was no corresponding decrease in methane consumption by the bacteria

Biotransformation of butachlor by soil fungi

Fusarium solani and Chaetomium globosum isolated from soil by enrichment techniques metabolized butachlor [2‐chloro‐2’,6'‐diethyl‐N‐(butoxymethyl) acetanilide] in the mineral salt solution. Whereas F. solani transformed butachlor into six metabolites, C. globosum formed four products. Out of these, several were new metabolites which were not reported earlier by F. solani, C. globosum or M. sufui. The structures of the metabolites were generally characterized by GC‐MS. The metabolism of this herbicide involved dechlorination, hydrolysis, dehydrogenation, N‐dealkylation, O‐dealkylation, C‐dealkylation and cyclization.

Unagglomerated powders for transformation-toughened structural ceramics

Results of a study of the characteristics of ZrO2 powders stabilized by 3 mol% Y2O3 and fabricated by the method of ultrasound spray pyrolysis from aerosols of aqueous solutions of mineral salts are presented. Unlike powders of the same composition obtained by the conventional coprecipitation technique, aerosol powders have coarser particles with a narrower size distribution and do not contain agglomerates. The temperature of sintering coarse aerosol powders to a maximum density is not high (1450°C). Despite the larger grain size in ceramics sintered from aerosol powders, their strength is much higher than that of ceramics obtained from ultradisperse coprecipitated powders of a similar composition.