Production of dextranase byLipomyces starkeyi

Summary The optimal growth rate ofLipomyces starkeyi, with dextran as sole carbon source, was found within the pH range 2.5–4.0, and temperature between 25–30°C. This yeast was unable to grow above 33°C. Dextranase production optima paralleled growth optima, except at pH 2.5. Decrease in enzyme yield at this pH could not be attributed to poor yeast growth or enzyme stability.     

High activity xylanase from thermotolerantStreptomyces T7: Cultural conditions and enzyme properties

Summary A thermotolerantStreptomyces T₇ produced 70–72 U/ml of extracellular xylanase activity when grown at 50°C in submerged culture, in à medium containing 5% wheat bran as a carbon source. Among the various sugars tested, maltose showed the highest activity of 8 U/ml. Pure xylan was less effective as an inducer as compared to wheat bran. Ammonium sulphate at a concentration of 0.7% was found to be optimum for maximum yield of the enzyme. The optimum period and pH for maximum production were 72th and 7.0, respectively. The culture filtrate was devoid of amylase, cellulase and B-xylosidase activity. The xylanase was exceptionally stable and did not show any loss in activity after storage at 50°C at pH 5.0 for 6 days.     

Partial characterization ofAspergillus fumigatus polygalacturonases for the degumming of natural fibers

Summary Aspergillus fumigatus strain 4, cultured on citrus pectin as the sole carbon source, produced polygalacturonases whose activity was optimum at 65°C and pH 3.5–4.5. The enzymes presented a bimodal thermostability for 10 min, but not 60 min, of incubation. Polygalacturonases showed pH stability between 3.0 to 9.0. The enzymes were stable when stored at 4–6°C for 90 days, but their activity was reduced by 24% when they were stored at 26–30°C. Orange pulp was the best pectic carbon source tested for the production of pectinases capable of retting ramie fibers. The reutilization of these enzymes was possible, suggesting the viability of industrial use of pectinases for degumming ramie fibers.     

Xylanase ofChaetomium cellulolyticum: Its nature of production and hydrolytic potential

Summary Maximum xylanase production byChaetomium cellulolyticum was obtained in the culture supernatant after 30 h of growth at 37°C in basal medium containing 1% xylan at pH maintained between 6.5 and 7.5. Addition of 0.05% Tween 80 to the medium increased the enzyme production considerably. Xylanase production was found to be growth associated. The optimal conditions for enzymatic hydrolysis of xylan were found to be pH 6.0 and 50°C. During enzymatic hydrolysis, xylose, xylobiose and other xylooligosaccharides were liberated from xylan. The pH values for xylanase production and for xylan hydrolysis were closely related to the utilization of hemicelluloses of aspen wood for fungal protein production by this organism as reported in our earlier work.     

Effluent treatment by anAzotobacter sp.

Summary The effect of pH, temperature and carbon source on the specific growth rate of anAzobacter sp. was studied in nitrogen-deficient media. The optimum pH and temperature were 7.0 and 30°C respectively, with COD removal 27–85%. The strain was also used for treating effluents of a pharmaceutical industry, with 37–45% COD removal.     

Improved xylanase production from a haloalkalophilic Staphylococcus sp. SG-13 using inexpensive agricultural residues

The production of an alkali-stable xylanase, with dual pH optima, from haloalkalophilic Staphylococcus sp. SG-13 has been enhanced using agro-residues in submerged fermentation and a biphasic growth system. The agro-residues such as wheat bran, sugarcane bagasse, corncobs and poplar wood when used as sole carbon source, improved the xylanase yield by five-fold as compared to xylose and xylan. Staphylococcus sp. SG-13 also produced equally good amounts of xylanase when grown simply in deionized water (pH 8.0) supplemented with agro-residues as sole carbon source. In the biphasic growth system (lower layer containing agricultural residue set in agar medium with liquid medium above it), the prime substrate, wheat bran (1% w/v), resulted in maximum xylanase production of 4525 U l^–1 (pH 7.5) and 4540 U l^–1 (pH 9.2) at an agar: broth ratio of 4.0 after 48 h of incubation at 37 °C under static conditions. In general, the cost-effective agro-residues were found to be more suitable inducers for xylanase production over expensive substrates like xylan.     

Enzymatic properties of lipase and characteristics production byLactobacillus delbrueckii subsp.bulgaricus

Some properties of an extracellular lipase produced byLactobacillus delbrueckii subsp.bulgaricus were studied. Maximum enzyme activity was found against olive and butter oil as enzyme substrates. Addition of 9% acacia gum, 0.1% Na-deoxycholate and 0.01 M CaCl₂ to the enzyme reaction mixture increased-lipase activity from 5.3 to 14.5 (FFA/mg protein/minute) at pH 6.0 and at 40° C. Maximum lipase production was reached in the presence of glucose as a sole source of carbon, wheat bran as nitrogen source, olive oil as a sole lipid source and butyric acid as fatty acid supporting the growth medium. An initial pH value of the culture medium of 6.0 and a temperature of 35° C gave the highest lipolytic activity.     

Ethanol production from glucose byClostridium thermosaccharolyticum strains: Effect of pH and temperature

Summary The fermentation of glucose byClostridium thermosaccharolyticum strains IMG 2811^T, 6544 and 6564 was studied in batch culture in a complex medium at different temperatures in defined and free-floating pH conditions. All the strains ferment 5 g glucose.l^–1 completely. The yield of the fermentation products turned out to be independent of the incubation temperature for strain IMG 2811^T. Strain IMG 6544 produced at 60°C significantly more ethanol and less acetic acid, butyric acid, hydrogen gas and biomass than at lower temperatures. With strain IMG 6564, the opposite effect occurred: ethanol appeared to be the main fermentation product at 45°C; at 60°C less ethanol and more acetic acid, butyric acid and hydrogen gas was formed.Experiments, carried out with strain IMG 6564, at defined pH conditions (between 5.5 and 7) and different temperatures (45, 55 and 60°C) revealed no effect of the incubation temperature, but an important effect of the pH on the product formation. At pH 7, ethanol was the main fermentation product while minor amounts of hydrogen gas, acetic and butyric acid were produced. Lowering the pH gradually to 5.5 resulted in a decrease of ethanol and an increase of biomass, hydrogen gas, acetic, butyric and lactic acids. At pH higher than 7 no growth occurred. Similar conclusions could be drawn for strains IMG 2811^T and 6544.     

Physical factors influencing the production of strawberry aroma byPseudomonas fragi grown in skim milk

Summary The influence of temperature, agitation speed, pH and biomass on the synthesis of 19 metabolites contributing to a strawberry aroma was followed over a 72 h fermentation of skim milk byPseudomonas fragi. Amongst the major odor-active metabolites were ethyl butyrate, ethyl hexanoate, ethyl 2-hexenoate, ethyl crotonate, ethyl isovalerate and ethyl 2-methyl hexanoate. Up to 17 ppm of some of these metabolites were detected at 60 h of fermentation, approximately 36 h after the beginning of the stationary growth phase. The production of most odor-active metabolites was higher at 11°C and 150 RPM than at 15, 20 or 25°C and 200 or 250 RPM. The development of off-aromas was observed at high temperatures and at high agitation speeds.     

A thermostable lipase produced by a newly isolated <Emphasis Type="Italic">Geotrichum</Emphasis>-like strain,R59

Growth and production of lipase by a new Geotrichum-like strain, R59, were studied. Production of extracellular lipase was substantially enhanced when the initial pH of the culture medium, types of carbon and nitrogen sources, substances probably stimulating the lipase biosynthesis, the temperature, and time of growth were optimized. Sucrose and triolein were the most effective carbon sources for lipase production. Maximum lipase activity (146 U/ml^–1) was obtained with urea as the nitrogen source. Growth at 30°C, an initial pH of 6.0 and incubation time of 48 h were found as optimum conditions for cell growth and production of lipase by Geotrichum-like strain R59. The enzyme was thermostable and exhibited very high activity after 1 h incubation at 60°C.     

Degradation of pyrene byRhodococcus sp. UW1

Summary A Rhodococcus species, designated strain UW1, was isolated from contaminated soil using conventional enrichment and isolation techniques. The isolate was able to use pyrene as sole source of carbon and energy; it mineralized 72% of the pyrene within 2 weeks. During growth a metabolite was detected in the culture fluid and further characterized by UV- and mass spectrometry. There is evidence that this metabolite resulted from a recyclization of the direct meta-ring-fission product of pyrene after dihydroxylation in either the 1,2- or 4,5-position. At pH 7.0 and 30°C Rhodococcus sp. UW1 showed a maximum degradation rate of 0.08 mg pyrene/ml per day, while growing with a doubling time of 30 h. The activity of the initial dioxygenase system was characterized by measuring the oxygen-consumption rates of pyrene-induced resting cells, the maxima of which occurred at pH 7.2 and 45°C. Rhodococcus sp. UW1 could also use phenathrene, anthracene, fluoranthene and chrysene as sole sources of carbon and energy, whereas naphthalene, dibenzofuran, fluorene and dibenzothiophene were only co-metabolized. Offprint requests to: U. Walter     

Metabolism of acrylonitrile by Klebsiella pneumoniae

A gram-negative rod-shaped bacterium capable of utilizing acrylonitrile as the sole source of nitrogen was isolated from industrial sewage and identified as Klebsiella pneumoniae. The isolate was capable of utilizing aliphatic nitriles containing 1 to 5 carbon atoms or benzonitrile as the sole source of nitrogen and either acetamide or propionamide as the sole source of both carbon and nitrogen. Gas chromatographic and mass spectral analyses of culture filtrates indicated that K. pneumoniae was capable of hydrolyzing 6.15 mmol of acrylonitrile to 5.15 mmol of acrylamide within 24 h. The acrylamide was hydrolyzed to 1.0 mmol of acrylic acid within 72 h. Another metabolite of acrylonitrile metabolism was ammonia, which reached a maximum concentration of 3.69 mM within 48 h. Nitrile hydratase and amidase, the two hydrolytic enzymes responsible for the sequential metabolism of nitrile compounds, were induced by acrylonitrile. The optimum temperature for nitrile hydratase activity was 55°C and that for amidase was 40°C; both enzymes had pH optima of 8.0.Abbreviations PBM phosphate buffered medium - GC gas chromatography - GC/MS gas chromatography/mass spectrometry     

Physiology of a Methanobacterium strain AZ

A methanogenic bacterium using H₂ and CO₂ as sole energy and carbon source has been isolated in pure culture from digested sludge. Its colonies on mineral agar are translucent, convex, circular with entire margins and yellow to brownish in colour. Cells are gram-positive, non motile and appear as straight cods, normally about 3 m long. A marked pleomorphism depending on the media was observed. The organism is chemolithoheterotrophic, has a pH optimum of 7.0 and an optimal temperature for growth of 33–40°C; no growth occurs above 45°C. The generation time at optimal conditions is less than 5 h. Cysteine must be supplied in the growth medium. It can act as sole sulfur source. The addition of sulfide accelerates the growth at an optimum concentration of 10^-4 to 10^-5 molar. A growth factor, not identical with SH-coenzyme M, occurring in anaerobic sewage sludge and yeast extract shows a stimulatory effect. 7.0–8.2% of the total carbon dioxide uptake is assimilated and 11.2% of the energy obtained from the reduction of carbon dioxide to methane is refound in the caloric value of the biomass. 0.01 ppm of dissolved oxygen completely inhibits growth and methane production. However, the bacteria do not loose their viability when exposed to high oxygen concentrations. Further informations are needed before this organism (DSM 744) is specifically identified.List of Abbreviations TOC total organic carbon - DOC dissolved organic carbon - POC particulate organic carbon     

<Emphasis Type="Italic">Paenibacillus</Emphasis> strain MP-1: a new source of mutanase

A mutan-degrading bacterium, closely related to Paenibacillus curdlanolyticus, was isolated from soil. It produced 0.4 U mutanase ml⁻¹ in 2 days in shake-flask cultures when bacterial mutan was the sole carbon source. Mutanase activity was optimal at pH 6.2 and 45°C over 1 h and was stable between pH 5.8 and 12 at 4°C for 24 h and up to 40°C for 1 h. Mutan produced by Streptococcus mutans was rapidly hydrolyzed by this enzyme. The hydrolysis of mutan (1 g l⁻¹) resulted in 17% saccharification over 2 h and, at the same time, glucan was entirely solubilized.     

Optimizing production of extracellular lipase fromRhodotorula glutinis

Production of extracellular lipase byRhodotorula glutinis was substantially enhanced when the type and concentration of carbon and nitrogen source, the initial pH of culture medium and the growth temperature were consecutively optimized. Lipase activity as high as 30.4 U/ml of culture medium was obtained at optimum conditions, comparing favourably with most of the activities reported for other lipase hyperproducing microorganisms. The enzyme was optimally active at pH 7.5 and 35°C and had, at optimum pH, half-lives of 45 and 11.8 min at 45 and 55°C respectively. The high activity and kinetic characteristics of the enzyme make this process worthy of further investigation.     

Production and properties of fibrinolytic enzyme fromStreptomyces sp. NRC 411

Of 16Streptomyces spp. investigated for the production of extracellular fibrinolytic enzyme, one species was chosen as the most promising producer. Using shaken cultures grown for 7 days, optimal conditions for enzyme production were pH 6.0, 5% (w/v) starch as carbon source, (NH₄)₂SO₄ and soybean flour as nitrogen sources and KH₂PO₄ at 1.2 g/l. Maximal activity of the crude enzyme was at pH 6.0 and 45°C. Holding the enzyme at 37°C for 2 h decreased the activity by only 10%.     

Biodegradation of toluene by the new fungal isolates Paecilomyces variotii and Exophiala oligosperma

Two new fungal strains, namely Paecilomyces variotii and Exophiala oligosperma, were isolated on toluene as the sole carbon and energy source, mineralizing the substrate into carbon dioxide. Fungal strains isolated so far on such a pollutant and completely degrading it are very scarce. Both fungi degraded the pollutant over the pH range 3.9–6.9 and temperature range 23–40°C, but E. oligosperma was barely active at the highest temperature of 40°C. Fungal growth on alkylbenzenes at 40°C has not been reported before. Since the activity of the strains gradually decreased at pH values below 4.0, the use of nitrate instead of ammonium was tested. In the presence of toluene, nitrate was a suitable nitrogen source for the Exophiala strain, but not for the Paecilomyces strain. Nitrate rather than ammonium allowed the maintenance of a more constant pH.     

Degradation of polycyclic aromatic hydrocarbons and long chain alkanes at 6070 °C by Thermus and Bacillus spp

Although polycyclic aromatic hydrocarbons (PAH) and alkanesare biodegradable at ambient temperature, in some cases low bioavailabilities are thereason for slow biodegradation. Considerably higher mass transfer rates and PAH solubilities and hence bioavailabilities can be obtained at higher temperatures. Mixed and pure cultures of aerobic, extreme thermophilic microorganisms (Bacillus spp., Thermus sp.) were used to degrade PAH compounds and PAH/alkane mixtures at 65 °C. The microorganismsused grew on hydrocarbons as sole carbon and energy source. Optimal growthtemperatures were in the range of 60–70 °C at pH values of 6–7. The conversion of PAH with 3–5 rings (acenaphthene, fluoranthene, pyrene, benzo[e]pyrene) was demonstrated. Efficient PAH biodegradation required a second, degradable liquid phase. Thermus brockii Hamburg metabolized up to 40 mg (l h)^-1 pyrene and 1000 mg(1 h)^-1 hexadecane at 70 °C. Specific growth rates of 0.43 h^-1 were measured for this strain with hexadecane/pyrene mixtures as the sole carbon and energy source in a 2-liter stirred bioreactor. About 0.7 g cell dry weight were formed from 1 g hydrocarbon. The experiments demonstrate the feasibility and efficiency of extreme thermophilic PAH and alkane biodegradation.     

Selection of yeast able to produce ethanol from glucose at 40° C

Summary A total of 55 yeast strains selected from 7 genera known to ferment carbohydrates to ethanol were screened for their ability to ferment glucose to ethanol in shaken flask culture at 37°, 40° and 45°C. Yields of more than 50% of the theoretical maximum were obtained with 28 strains at 37°C, but only 12 at 40°C. Only 6 could grow at 45°C, but they produced poor yields. In general Kluyveromyces strains were more thermotolerant than Saccharomyces and Candida strains, but Saccharomyces strains produced higher ethanol yields. The 8 strains with the highest yields at 40°C were evaluated in batch fermentations. Three of these, two Saccharomyces and one Candida, were able to meet minimum commercial targets set at 8% (v/v) ethanol from 14% (w/v) glucose at 40°C.     

Decolorization of azo dyes by Rhodobacter sphaeroides

Rhodobacter sphaeroides AS1.1737 decolorized more than 90% of several azo dyes (200 mg dyes l^–1) in 24 h. The optimal culture conditions were: anaerobic illumination (1990 lx), peptone as carbon source, temperature 35–40 °C and pH 7–8. Intracellular crude enzyme from this strain had azoreductase activity, optimized temperature as 45–50 °C, and decolorization kinetics which were consistent with a ping-pong mechanism.