pH Of Fermentation Medium Research Articles

Optimization of Bioethanol Production by Enzymatic Hydrolysis and Fermentation From Rind Cocoa Fruit (Theobroma Cacao L)

Cocoa (Theobroma cacao L) production in Indonesia based on data from the Central Statistics Agency (BPS) for 2020 reached 720.66 thousand tons and continues to increase every year. Increasing cocoa production can cause cocoa waste to increase as well. Cocoa waste handling can be overcome by producing bioethanol as a way to reduce the amount of waste produced. This study aims to utilize cellulose compounds from cocoa fruit waste in the production of bioethanol through several stages, namely delignification, enzymatic hydrolysis by cellulase enzymes and the fermentation process with the help of Zymomonas mobilis bacteria. The results showed that the lignin level decreased by 19.5%, the hemicellulose level decreased by 6.87% and the cellulose level increased by 27.45%. Hydrolysis and fermentation stages were analyzed using the response surface method (RSM) to obtain optimum conditions. Cellulose can be optimally hydrolyzed using a pH buffer of 2 and a temperature of 30°C with a glucose concentration of 21,703 mg/mL. The fermentation process can be carried out at optimum conditions using a fermentation medium pH 10 with an incubation time of 168 hours. The bioethanol level was analyzed using a refractometer and gas chromatography (GC) with a yield of 8.43% (v/v).

Differential effects of rapeseed, sunflower and linseed oils on rumen microbial functions in dual effluent fermenters on maize silage-based diet

Quantitative information on the concurrent changes in major rumen microbial functions induced by dietary lipids in relation with the degree of unsaturation of fatty acids is scarce. During a three-period essay (9 days per period), rapeseed (Brassica napus L., RO), sunflower (Helianthus annuus L., SO) and linseed (Linum usitatissimum L., LO) oils at the high level of 80 g/kg dry matter input (DMI) and a control without oil were compared in four 1-L dual outflow fermenters inoculated with bovine rumen microbiota and maintained on a maize silage-based diet. Neither the fermentation medium pH and redox potential nor starch and protein degradabilities were significantly altered. Oil supply significantly decreased butyrate and methane specific productions of to the benefit of propionate and hydrogen specific productions and decreased the microbial protein outflow and synthesis efficiency while increasing the outflows of ammonia and isovalerate, these effects being amplified by the fatty acids’ unsaturation degree. Besides, with no impact of the degree of unsaturation, oil supply increased the amount of fermented hexose, the productions of all SCFAs except butyrate and the specific production of acetate. The rumen variables apparently sensitive to oil unsaturation degree were thus related either to metabolic hydrogen removal pathways or to protein metabolism.

Conversion of Waste Cooking Oil to Rhamnolipid by a Newly Oleophylic Pseudomonas aeruginosa WO2.

The components of waste cooking oil (WCO) are complex and contain toxic substances, which are difficult to treat biologically. Pseudomonas aeruginosa WO2 was isolated from oily sludge by an anaerobic enrichment–aerobic screening method, which could efficiently utilize WCO and produce rhamnolipid. The effects of nutrients and culture conditions on bacterial growth and lipase activity were investigated to optimize the fermentation of WCO. The results showed that strain WO2 utilized 92.25% of WCO and produced 3.03 g/L of rhamnolipid at 120 h. Compared with inorganic sources, the organic nitrogen source stabilized the pH of fermentation medium, improved lipase activity (up to 19.98 U/mL), and promoted the utilization of WCO. Furthermore, the WO2 strain exhibited inferior utilization ability of the soluble starch contained in food waste, but superior salt stress up to 60 g/L. These unique characteristics demonstrate the potential of Pseudomonas aeruginosa WO2 for the utilization of high-salinity oily organic waste or wastewater.

Porcine in vitro fermentation characteristics of canola co-products in neutral and acidic fermentation medium pH

An in vitro study was conducted to determine effects of reducing pH of porcine in vitro fermentation medium on compositions of glucosinolate degradation products and porcine in vitro fermentation characteristics for solvent-extracted canola meal (SECM) and cold-pressed canola cake (CPCC). Two canola co-products were subjected to porcine in vitro fermentation for 72 h. Accumulated gas production during microbial fermentation was recorded and modeled to estimate kinetics of gas production. Glucosinolate degradation products after microbial fermentation were determined and fermentation medium pH after incubation was recorded. Total and individual volatile fatty acids (VFA) concentrations per unit weight of dry matter (DM) of feedstuffs were determined. On DM basis, SECM and CPCC contained 6.15 and 11.1 µmol/g of glucosinolates, respectively. Goitrin concentration for CPCC was lower (P < 0.05) than that for SECM. Isothiocyanate and indole-3-acetonitrile concentrations for CPCC were lower (P < 0.05) than those for SECM, whereas thiocyanate concentration for CPCC was greater (P < 0.05) than that for SECM. A reduction in fermentation medium pH from 6.2 to 5.2 increased (P < 0.05) goitrin and indole-3-acetonitrile concentrations and decreased (P < 0.05) isothiocyanates concentration for SECM, but did not affect concentration of these 2 glucosinolate degradation products for CPCC. Fermentation medium pH after in vitro fermentation for SECM tended to be greater (P = 0.081) than that for CPCC. Canola co-product type and fermentation medium pH did not interact on gas production parameters. However, a reduction in fermentation medium pH from 6.2 to 5.2 resulted in increased (P < 0.05) lag time and reduced (P < 0.05) fractional rate of degradation and total gas production. Canola co-product type and fermentation medium pH did not interact on total or individual VFA production per gram of DM of feedstuff fermented. However, reducing fermentation medium pH from 6.2 to 5.2 increased (P < 0.05) total VFA and acetate productions, and tended to reduce (P = 0.083) branched-chain VFA production SECM and CPCC. In conclusion, a reduction in fermentation medium pH from 6.2 to 5.2 resulted in increased production of goitrin and indole-3-acetonitriles from SECM-derived glucosinolates, but did not affect production of thiocyanate from SECM-derived glucosinolates. Glucosinolates in CPCC were less affected by the fermentation medium pH used in the current study. It appears that there are other factors other than pH that affect the degradation of canola-derived glucosinolates by microorganisms from hindgut of pigs.

Utilization of Whey for Red Pigment Production by Monascus purpureus in Submerged Fermentation

Various biotechnological approaches have been employed to convert food waste into value-added bioproducts through fermentation processes. Whey, a major waste generated by dairy industries, is considered an important environmental pollutant due to its massive production and high organic content. The purpose of this study is to investigate the effect of different fermentation parameters in simultaneous hydrolysis and fermentation (SHF) of whey for pigment production with Monascus purpureus. The submerged culture fermentation parameters optimized were type and pretreatment of whey, pH, inoculation ratio, substrate concentration and monosodium glutamate (MSG) concentration. Demineralized (DM), deproteinized (DP), and raw whey (W) powders were used as a substrate for pigment production by simultaneous hydrolysis and fermentation (SHF). The maximum red pigment production was obtained as 38.4 UA510 nm (absorbance units) at the optimized condition of SHF. Optimal conditions of SHF were 2% (v/v) inoculation ratio, 75 g/L of lactose as carbon source, 25 g/L of MSG as nitrogen source, and fermentation medium pH of 7.0. The specific growth rate of M. purpureus on whey and the maximum pigment production yield values were 0.023 h−1 and 4.55 UAd−1, respectively. This study is the first in the literature to show that DM whey is a sustainable substrate in the fermentation process of the M. purpureus red pigment.

Effect of growth conditions on β-glucosidase production by local isolate of Aspergillus niger using rice bran substrate

Abstract. Sugiwati S, Hanafi M, Lioe HN, Suhartono MT. 2020. Effect of growth conditions on β-glucosidase production by local isolate of Aspergillus niger using rice bran substrate. Biodiversitas 21: 4058-4066. β-Glucosidase is the family of glycosyl hydrolase that have potential role in various food industry, such as in tea, wine and vanilla industries to increase the aroma and production of isoflavone aglycons in soybean flour. The present work produced β-glucosidase from local isolate of Aspergillus niger InaCC F57 under solid-state fermentation (SSF) using rice bran substrate. Fermentation process was made in various conditions with respect to carbon source as substrate, initial pH of fermentation medium, incubation time, water to substrate ratio, fermentation temperature, and addition of Mandels mineral salts solution. The results showed that activity of β-glucosidase was best at, i.e., 2.45 U/mL, with the use of rice bran as substrate. Furthermore, optimum condition for the highest production of β-glucosidase occurred at pH 2.0, incubation time of 5 days, water to substrate ratio of 1.5: 1, and incubation temperature of 32°C. Additionally, in optimum fermentation conditions, production of β-glucosidase could be enhanced up to 26.22% with the presence of Mandels mineral salts solution as compared to the control.

Green polygalacturonase production by Aspergillus awamori NRC-F18 under solid-state fermentation

Background and objective Pectin-degrading enzymes applied in the food industries are preferred to be obtained from fungal origin because fungi are potent producers of pectic enzymes and the optimal pH of fungal enzymes is very close to the pH of many fruit juices, ranging from pH 3.0 to 5. Pectinolytic enzymes, have several industrial applications in different industries such as food industries to concentrate fruit juices. They increased the yield of fruit juice from the pulp and removal of haze from juices to get a clear product. Research to find microorganisms to produce high-quality polygalacturonase (PGase) and technical constraint include supply of cheap and pure raw materials needed to produce inexpensive enzymes. Utilization of agroindustrial residues offers potential benefits for solid-state fermentation, which is attractive for the implementation of sustainable bioprocesses.Materials and methods Fungal strain screening for PGase production was studied in 250 ml Erlenmeyer flasks containing 5 g of tested substrate moistened to 50% (v/w, ml/g) with distilled water. One milliliter of spore suspension (106 spores) from each fungus was used as inoculum. The cultures were incubated at 30°C for 4 days. At the end of the incubation period, 100 ml of distilled water was added to each flask, blended by shaking at 150 rpm for 30 min, and harvested by filtration. The filtrates were saved as sources of crude enzyme. The selected fungal strain and substrate were incubated for 120 h at 30°C and culture was taken at 24 h intervals to detect the optimum incubation period. Sugar beet pulp was moistened to different moisture levels, that is, 1 : 1, 1 : 2, 1 : 3, and 1 : 4 (v/w) under the optimum incubation period to determine the more suitable moisture content for enzyme production. Sodium phosphate buffer at 0.1 M was used for adjusting the initial pH of fermentation medium to different values from 3.5 to 7.5 to study the effect of pH on enzyme secretion. The fungus was incubated under different temperatures, that s, 20, 25, 30, 35, and 40°C to study the temperature effect on enzyme production. Inorganic nitrogen sources (at level 0.92 mg N/g solid substrate) were applied in the fermentation medium to study their effect on enzyme yield.Results and conclusion Aspergillus awamori NRC-F18 showed promising PGase’ production activity than other fungi screened. The study showed that the fungus gave promising results when the moisture content was adjusted to 70% (v/w), initial pH value 5.0, and incubation temperature at 35°C for 72 h. The enzyme activity was increased when urea was the sole nitrogen source at a level of 0.92 mg/g solid substrate supplemented to fermentation medium. Under the above conditions, 396.4 U/g original substrate was obtained. A study on the obtained PGase revealed that it has an optimum pH that ranged from 4.5 to 5.5, as well as it gave the highest activity when incubated at 50°C. Eighty percent ammonium sulfate (w/v) was applied to precipitate enzyme protein, as 24% of total protein involved 61% of total PGase activity obtained with a specific activity of 36.94 U/mg protein against 12.8 U/mg protein in the crude culture supernatant. After fermentation the mixture from unutilized raw material and fungal biomass after enzyme elution was 76% (w/w) from the original substrate dry weight involving 14.2% protein related to 9.2% before beet pulp fermentation which could be utilized as feedstuff component in rations for ruminant feed.

Optimized pH and Its Control Strategy Lead to Enhanced Itaconic Acid Fermentation by Aspergillus terreus on Glucose Substrate

Biological itaconic acid production can by catalyzed by Aspergillus terreus (a filamentous fungi) where the fermentation medium pH is of prominent importance. Therefore, in this work, we investigated what benefits the different pH regulation options might offer in enhancing the process. The batch itaconic acid fermentation data underwent a kinetic analysis and the pH control alternatives were ranked subsequently. It would appear that the pH-shift strategy (initial adjustment of pH to 3 and its maintenance at 2.5 after 48 h) resulted in the most attractive fermentation pattern and could hence be recommended to achieve itaconic acid production with an improved performance using A. terreus from carbohydrate, such as glucose. Under this condition, the itaconic acid titer potential, the maximal itaconic acid (titer) production rate, the length of lag-phase and itaconic acid yield were 87.32 g/L, 0.22 g/L/h, 56.04 h and 0.35 g/g glucose, respectively.

Effect of extruded linseed supplementation, grain source and pH on dietary and microbial fatty acid outflows in continuous cultures of rumen microorganisms

Using 6 continuous cultures of rumen microorganisms, we studied the effects of pH (low vs. high) and extruded linseed supplementation (10% of DM) in association with rapidly or slowly degraded starch sources (wheat vs. corn grains) 1) on fatty acid (FA) outflows and PUFA biohydrogenation (BH) processes 2) on FA microbial composition and its contribution to FA outflows, in two replicated periods of 10d (7d adaptation and 3d sampling). The control diet contained wheat. The buffer solutions infused in low or high pH cultures differed by the addition of 10 mL of 5 N H2SO4 or NaOH so as to allow fermentation medium pH fluctuations with diets and time after feeding. The fermentation pattern, daily amounts of hexoses fermented (HF), efficiency of microbial protein synthesis (EMPS), and specific production of gases (CH4 and H2) were measured. FA compositions were determined in total effluents and bacterial pools isolated from effluents. Lowering pH (from 6.46 to 6.16 measured just before feeding) increased the VFA concentration in the control diet whereas it decreased it in all linseed supplemented diets. Lowering pH tended to decrease CH4 specific production as well as acetate and propionate proportions and to increase butyrate and valerate proportions but did not alter HF and EMPS. Linseed but not grain source increased pH by 0.08 and did not modify fermentative parameters. Apparent BH of C18:3 9c,12c,15c and C18:2 9c,12c decreased at low pH but increased with linseed supplementation. Corn associated to linseed increased 18:3 9c,12c,15c BH compared to wheat. Consequently, C18:3 9c,12c,15c outflows increased at low pH and with linseed, and were higher with linseed-wheat diet than linseed-corn diet. For all treatments, the proportions of C18:0 (% of C18-FA outflows) remained low associated with high levels of BH intermediates (C18:2 11t, 15c and C18:1 11t) suggesting that BH did not proceed to completion. Lowering pH decreased C16:1 9c and C18:1 11c bacteria contents and tended to increase anteiso-FA. Linseed supplementation increased C18:0, C18:1 9c, C18:1 9t, C18:2 9c,12c bacteria contents without modifying the C18:3 9c,12c,15c and decreased their odd-FA content and anteiso-FA in tendency. Compared to wheat, corn decreased branched-FA bacteria content, as well as even-saturated FA. Lowering pH decreased the bacterial FA outflow whereas linseed increased it. Both decreased the bacterial FA contribution to total FA outflow. Results indicate that pH and diets modified PUFA BH while differing in their effect on odd- and branched-chain FA bacteria content and outflows.

Producción de Hidrógeno a partir de la fermentación de residuos agroindustriales de la piña

&lt;p&gt;Se estudió la generación de hidrógeno a partir de la fermentación anaeróbica de residuos agroindustriales de corazón de piña utilizando como inóculo lodos pretratados provenientes de una planta de tratamiento de agua residual del tipo UASB. Mediante un diseño factorial 23, se determinaron los efectos de la concentración inicial de sustrato, del pH inicial del medio de fermentación y de la formulación de nutrientes, sobre el rendimiento en la producción de hidrógeno. Los mejores resultados se obtuvieron utilizando un pH inicial de 5,5, con una concentración inicial de sustrato de 5 (g de glucosa)/L y usando una formulación de nutrientes basada en magnesio, hierro, zinc y sodio. Posteriormente, utilizando las condiciones de operación anteriores, se realizó un escalamiento de la fermentación en un bioreactor de 5 L y se alcanzó un rendimiento máximo en la producción de hidrógeno de 1,541 (mol H2)/(mol glucosa). Este rendimiento es comparable con datos reportados en la literatura cuando se ha usado glucosa como sustrato. Los resultados obtenidos sugieren que los residuos de corazón de piña podrían ser utilizados como una fuente renovable para la producción de hidrógeno.&lt;/p&gt;

Study the influence of culture conditions on rennin production by Rhizomucor miehei using solid-state fermentations.

Investigations were conducted on the production of Rennin enzyme from the fungi Rhizomucor miehei 3420 NRRL using Solid-State fermentation. Wheat bran was used as a substrate. The influence of moisture content, incubation temperature, and the initial pH of fermentation medium were studied. The protein content, milk clotting activity (MCA), specific activity, proteolytic activity (PA), and (MCA/PA) ratio of the extracted enzyme were calculated after 4 days of incubation to evaluate the quality of the enzyme. The results showed that the optimal conditions for production were as follows: incubation temperature of 40 °C, moisture content of 60%, and pH of (3). Under these conditions, a production process of Rennin enzyme was established, and the values of protein content, milk clotting activity, specific activity, proteolytic activity, and (MCA/PA) ratio reached to 4 mg/mL, 600 SU/mL, 150 SU/mg, 45 PU/mL, 13.3 respectively.

Citric Acid Production from Nontreated Beet Molasses by a Novel Aspergillus niger Strain: Effects of pH, Sugar and Ingredients

Effects of factors on the citric acid production from non-treated beet molasses were studied in Aspergillus niger OE55. Maximum amount of citric acid (19.13 and 34.62 g/L) was achieved when the initial pH of fermentation medium was 6.0 from 200 g/L and 150 sugar respectively. Citric acid production and biomass formation continuously increased during fermentation period in the media initially containing 200 g/L sugar. Remaining sugar (from 3.20 to 6.03 g/L) was higher at the end of fermentation in the media initially containing 160 g/L sugar than 200 g/L sugar. Yield of citric acid after 4 days of fermentation were ranged from 0.16 to 0.28 g/g from 160 g/L sugar. The high phosphorus and nitrogen levels stimulated biomass formation and reduced citric acid production. The optimum incubation for maximal citric acid production varies both with the sugar concentration in non-treated molasses and fermentation conditions for the novel A. niger strain. pH of fermentation media cannot have reduced below 4.72 and 3.35 in the media containing 200 and 160 g/L sugar, respectively, during fermentation, therefore citric acid production was not increased over 19.96 and 34.58 g/L respectively. This would be due to the formation of nitrogenous and polysaccharide compounds from molasses. Strain development in the citric acid production from wild strains depends mainly on the fermentation conditions.

Simultaneous Saccharification and Fermentation of Banana (Musa cuminata) Peel for Bioethanol Production

Banana (Musa acuminata) peel is discarded after the fruit processing process. Banana peel biomass can be used as raw material to produce bioethanol. In this research, banana peel was fermented by simultaneous saccharification and fermentation using Saccharomyces cerevisiae. Production of bioethanol was determined and the effects of various operation conditions which included different parameters in fermentation process: fermentation time, temperature, medium pH, concentration of yeast, enzyme loading, and shaking period. peel was cut, pretreated with H2SO4 2% and simultaneous hydrolyzed and fermented. Ethanol production was greatest (over 10,5%) when the initial pH of fermentation medium was adjusted to 4.5, 5% yeast supplement (8x107 cfu/ml), 7% cellulase (100 IU, v/v) loading, 24 hours and 37oC incubating,. The results illustrated that the simultaneous accharification and fermentation (SSF) of banana peel with S.cerevisiae has potential for industrial application.

Thermo Stability Study of Crude Amylase from Bacillus Isolate

An amylolytic strain was collected from rotten potato and its activity evaluated. The isolated strain was cultivated for amylase production in shake flasks at 35±2oC and the fermentation pattern was studied. Optimum temperature for maximum enzyme synthesis was observed at 35°C, when initial pH of fermentation medium was adjusted to 5.5. Maximum extracellular amylase activity of 7.9 U/mL and the maximum intracellular activity of 320 U/mL was recorded. Although maximum biomass was present at 12.6 g/L but highest growth rate was observed between 08 to 40h with maximum at 36h. The extracellular amylase present in the broth was partially purified with an overall yield of 44% through purification procedure of ammonium sulphate precipitation. After completed extraction and partial purification and stabilization, the stability of enzyme was observed in a range of temperature and pH between 60°C-90°C and 2-8 pH respectively. Maximum enzyme activity was demonstrated at 90°C, and pH of 5.5 and 6.5. The thermo stability of the amylases of this Bacillus species was comparable to that of amylases from other microbial sources.Int J Appl Sci Biotechnol, Vol 3(3): 427-430

Production of lipases by Alternaria sp. (mbl 2810) through optimization of environmental conditions using submerged fermentation technique

The present investigation was conducted for the biosynthesis of extracellular and intracellular lipases by Alternaria sp. (MBL 2810) through submerged fermentation technique. To increase the lipases production various parameters were optimized such as nitrogen, carbon sources and additional additives besides the basic cultural conditions e.g., rate of fermentation, volume of fermentation medium, inoculum size and type and initial pH of fermentation medium. The maximum extracellular and intracellular lipases production was achieved, when fermentation was optimized at room temperature for 24 h at the agitation speed of 100 rpm. Other cultural conditions such as inoculum type and inoculum size (4.0 mL) was also optimized, glycine as an additional carbon source and urea as an additional nitrogen source gave the maximum extracellular lipases activity. Maximum production of extracellular lipases (9.04 ± 0.05 a U/mL) was achieved when volume of fermentation was optimized at 25mL and maximized intracellular lipases (10.04 ± 0.13a U/mL) production was achieved when the medium pH was adjusted at 5.

Biohydrogen production from normal starch wastewater with heat-treated mixed microorganisms from a starch factory

Biohydrogen production was studied from normal starch factory wastewater of approximately 20,000 mg chemical oxygen demand (COD)/l with heat-treated mixed microorganisms originating from the plant. Acclimated heat-treated microorganisms that produced H2 50% during the acclimation period were used as the parent culture. Experiments were performed in a batch and semi-continuous operation through dark fermentation. The results found that normal starch wastewater can be the sole carbon source for biohydrogen. For batch operation, the maximum hydrogen yield and specific hydrogen production rate of 250 ml at standard temperature and pressure (STP)/g COD degraded and 13.9 ml at STP/g cells-hour were obtained when operating the system at initial wastewater pH 4. For semi-continuous operation, the maximum hydrogen yield of 100 ml at STP/g COD degraded was obtained when operating the system at an organic loading rate of 28.6 kg COD/m³-day or a hydraulic retention time of 18 hours. The fermentation medium pH should not be much higher than pH 5 during digestion.

&lt;b&gt;Effect of initial pH in levan production by &lt;i&gt;Zymomonas mobilis&lt;/i&gt; immobilized in sodium alginate&lt;b&gt;

Zymomonas mobilis was immobilized using a cell suspension fixed to 8.6 x 107 CFU mL-1 by spectrophotometry. This biomass was suspended in sodium alginate solution (3%) that was dropped with a hypodermic syringe into 0.2 M calcium chloride solution. Was test two initial pH of fermentation medium (4 and 5) and different sucrose concentrations 15, 20, 25, 30 and 35% at 30˚C, without stirring for 24, 48, 72 and 96 hours. The levan production to pH 4 was high in sucrose 25% for 24 (16.51 g L-1) and 48 (15.31 g L-1) hours. The best values obtained to pH 5 was in sucrose 35% during 48 (22.39 g L-1) and 96 (23.5 g L-1) hours, respectively. The maximum levan yield was 40.8% and 22.47% in sucrose 15% to pH 4 and 5, respectively. Substrate consumption to pH 4 was bigger in sucrose 15 (56.4%) and 20% (59.4%) and to pH 5 was in 25 (68.85%) and 35% (64.64%). In relation to immobilization efficiency, Zymomonas mobilis showed high adhesion and colonization in support, indicated by cell growth increased from 107 to 109 CFU mL-1 during fermentation time.

Optimization of bioethanol production from glycerol by Escherichia coli SS1

Bioethanol is a promising biofuel and has a lot of great prospective and could become an alternative to fossil fuels. Ethanol fermentation using glycerol as carbon source was carried out by local isolate, ethanologenic bacterium Escherichia coli SS1 in a close system. Factors affecting bioethanol production from pure glycerol were optimized via response surface methodology (RSM) with central composite design (CCD). Four significant variables were found to influence bioethanol yield; initial pH of fermentation medium, substrate concentration, salt content and organic nitrogen concentration with statistically significant effect (p ≤ 0.05) on bioethanol production. The significant factor was then analyzed using central composite design (CCD). The optimum conditions for bioethanol production were substrate concentration at 34.5 g/L, pH 7.61, and organic nitrogen concentration at 6.42 g/L in which giving ethanol yield approximately 1.00 mol/mol. In addition, batch ethanol fermentation in a 2 L bioreactor was performed at the glycerol concentration of 20 g/L, 35 g/L and 45 g/L, respectively. The ethanol yields obtained from all tested glycerol concentrations were approaching theoretical yield when the batch fermentation was performed at optimized conditions.

Isolation and Degradation Characterization of Trichloroethylene-Degrading Bacteria

Trichloroethylene is one of chlorinated organic compounds widely used as a solvent and degreasing agent in industry. Because of uninformed disposal in the past, trichloroethylene has become one of major contaminant in environment, and this situation has brought about a serious public concern for its toxicity. A promising approach to solving this problem is bioremediation using degrading-bacteria. A bacterium(strain TC-1) was isolated from environment, which could degrade trichloroethylene. It was preliminary identified as the genus of Sporosarcina sp.. The results showed that the optimal degradation temperature, degradation time, rotary speed and the initial pH of fermentation medium were 25°C, 60 h, 180 rpm and 7.5 respectively, the ratio of degradation reached 95.56% under this conditions.

Alpha-amylase production by toxigenic fungi

This study is concerned with the screening of Alternaria alternata (Fr.) Keissler and Alternaria tenuissima (Kunze ex Pers.) Wilts strains for the biosynthesis of α-amylases. Nine strains of A. alternata and three strains of A. tenuissima were grown on enzyme production medium (EPM) and potato dextrose agar (PDA) using three pH levels (4.5–6.5); then the selected strains, able to produce bigger zones of starch hydrolysis on solid media, were subjected the testing of their amylolytic efficacy in liquid medium. In primary screening, the amylolytic activity of all the strains was tolerant to a wide range of initial culture pH values (4.5–6.5). Of all the cultures tested, A. alternata strains FCBP-100 and FCBP-385, and A. tenuissima strains FCBP-183 and FCBP-252 exhibited the maximum potential in terms of starch hydrolysis at pH 4.5 on EPM, and hence were selected for further studies. In secondary screening, the optimum pH of fermentation medium was adjusted to 4.5 using 0.05 M citrate buffer for the estimation of amylolytic enzyme activities. At 48 h incubation, the maximum α-amylase activity (31.8 units mL−1) was discerned by A. tenuissima strain FCBP-252.