Salient parameters involved in mosquitocidal toxins production from bacillus sphaericus by semi-solid substrate fermentation

A Bacillus sphaericus strain 14N1 was isolated from Egyptian environments during the year 2002 that exhibited mosquitocidal activity higher than the international standard B. Sphaericus strain 2362. It was used for the production of mosquitocidal toxins using semisolid substrate fermentation [SSF] technology. This goal was achieved through a series of experimental studies aiming at the elucidation of the most important factors affecting growth parameters, CFU and spores counts and toxin production. These included sources of nutrients, type of carriers material, moisture content, aeration level, inoculum size, incubation period and response to additional nutritional supplements in terms of growth and sporulation parameters change and toxin productivity improvements. Among a group of finely ground agro-industrial by-products and legumes seeds used as substrates, the highest levels of toxins production were obtained using cotton seed meal, sesame seed meal followed by fodder yeast and linen seed meal. The optimum concentration of cottonseed meal in growth medium for mosquitocidal toxin production ranged between 3.0% and 6.0% [w/w]. The highly coarse wheat bran was the optimum carrier material for mosquitocidal toxin production followed by beat moss, kaoline clay mineral and talcum powder. The moisture content of semisolid medium exerted great influence on toxin production reaching maximum values at 50% [w/w] followed by progressive decrease at higher moisture contents reaching virtually no toxin production at 80% [w/w]. Within the tested inoculum size, the use of 19 x 106 CFU/g solid medium favored the toxin production. The level of toxin production was fairly stable within a wide range of increasing air space available in the experimental flasks except at very large levels of air space where a notable decline was noted in toxin production probably due to moisture loss of the culture. Progressive increase in toxin production was noted with extending incubation periods of culture reaching maximum toxin production level after nine days growth period followed by decline in toxin level upon extended incubation periods. Supplementation of growth medium with suitable concentration of peptone, yeast extract as well as with mineral salt solutions increased the production of toxin levels several folds. Lower increases in toxin production levels were obtained upon the addition of concentrates of corn steep liquor. The obtained results were discussed in the light of application feasibilities of mosquitocidal toxin production by SSF technology at lower and affordable expenses in the developing countries

Production of fungal cellulases under static conditions for saccharification of lignocellulosic wastes in Egypt

Physiological studies were carried out for optimization of production of cellulases and beta-glucosidase by Penicillium funi-culosum NRCE-269. The highest levels of beta-glucosidase were obtained from statically incubated cultures, whereas the filter paper activity [FPA] was slightly lower as compared to that obtained in shake cultures. Under the static incubation adopted here, both enzymes were optimally produced in media with initial pH adjusted to 5.0. The filter paper activity and carboxymethl-cellulase activity [CMCA] were induced maximally by cellobiose, and xylose whereas beta -glucosidase activity was specifically induced by cellobiose. Several ligno-cellulosic wastes common in Egypt were tested with respect to their suitability for enzymes production. The alkalitreated corn cobs gave the highest levels of the three enzyme activities under study. Filtrates of cultures grown on corn cobs medium were used as enzyme sources for saccharification of alkali-treated rice straw, wheat straw and sugar-cane bagasse. The saccharification process was carried out at pH 4.8 and temperature 50° for 60 hr at 5% substrate concentration. Under the stated conditions, saccharification expressed as percentages of the dry weight of the three iignocellulo-sic wastes amounted to 53%, 59% and 70% respectively. These values corresponded to 81%, 76% and 73% of the content of available sugars in the three lignocellulosic wastes in the same order. The results obtained were discussed in the light of their application feasibility with special reference to the developing countries

Properties of crude beta-galactosidase of Mucor hemiclonus and its application in lactose hydrolysis of some dairy by-products

Biochemical studies on the properties of acetone precipitated extracellular beta-galactosidase of M. humicolus indicated that the enzyme is notably thermostable expressing maximum activity at 60° and pH 3.0. The reaction progress with time was linear up to 30 minutes of incubation. The enzyme could effectively hydrolyze lactose present in some dairy by-products. Thus upon using enzyme level of 0.9 unit/ml the enzyme could hydrolyze 28.8%, 32.4%, 62.4%, 18.2% and 43.1% of lactose present in milk, whey, 1: 1 diluted whey, whey permeate and 1: 1 diluted whey permeate respectively, after 8 hr at 30°. At 40° and at the same enzyme level the percentage of lactose hydrolyzed reached 60.0%, 63.6%, 69.6% and 70.0% in whey permeate, whey, diluted permeate and diluted whey respectively. At the same temp. [40°] and by increasing enzyme concen. to 1.8 unit/ml, the lactose hydrolysis reached 64.4%, 84.0%, 77.0% and 86.8% of lactose present in the four substrates respectively. The results are discussed in the light of the application feasibility of this enzyme

Taxonomic and ecophysiological studies on phyllospheric yeasts of triticum vulgare

Studies of some polysaccharides produced by the isolates revealed that Rhodotorula glutinis T1 form a copious extracellular heteropolysaccharide material. It was found to be composed to mannose, galactose and minor traces of glucuronic acid. On the other hand, Cryptococcus magnus T2 was found to produce starch-like compounds that are released outside the cells under low pH conditions and on a variety of sugars as carbon sources. The starch formation increased proportionally with glucose concentrations up to 10% final concentration after five days of growth. However, no correlation between the extent of growth and starch release could be detected

Production of single cell protein from food industry wastes: III Optimization of some culture conditions affecting fungal growth

The present study investigated some optimum growth conditions for producing maximum protein from two fungal cultures, namely; M. verrucaria, and T. viride grown in shaked culture using pretreated beet pulp as substrate. Both fungal cultures proved their ability to grow over a wide range of initial pH of the medium. Mycelial protein content reached its maximum by increasing inoculum ratio in medium to 2% for T. viride and to 8% M. verrucaria. Supplementation of growth medium by different organic and inorganic nitrogen sources promoted markedly protein production. Maximum values for mycelial protein content were obtained by using urea as a nitrogen source. However, both cultures differed in their response towards the concentration of urea in medium, T. viride was more sensitive to higher concentrations than the other culture. Results demonstrated that maximum protein production was obtained using 0.17% and 0.07% urea with M. Verrucaria and T. Viride, respectively. A study of the effect of aeration indicated that maximal values for mycelial protein content were given at air: Medium ratio of 5:3 and 5:2 with M. verrucaria and T. viride, respectively. Moreover, results revealed that mycelial protein content increased by increasing substrate concentration in the medium up to 10% and 20% beet pulp with M. verrucaria and T. Viride, respectively

Kinetics and properties of partially purified yeast B galactosidase produced in salted whey

The B-galactosidase enzyme of Kluyveromyces lactis NRRL-1118 grown in salted whey medium was obtained by solvent extraction and also by sonication of the cell for different periods. Best results were obtained by interrupted sonication for 20 min with cooling of the cells. The enzyme was purified 37 times by fractional precipitation using acetone and repeated centrifugation. The partially purified enzyme has optimum pH between 6.5-7.0 and Km 1.18 mM for ONPG as substrate. The enzyme was heat labile and exhibited maximum activity at 40 degree C. Notable activation of the enzyme was detected with manganese ion whereas little or no effect was observed for several cations

Characterization of renninlike enzyme produced in submerged culture of aspergillus niger

Aspergillus migor produced powerful milk - clotting activity when it was grown aerobically in submerged cultures. The enzyme could be produced in sweet rennet buffalo whey and in salted whey media without extraneous- supplementation with other nutrients. Characterization studies on the activity produced in sweet whey media have revealed that the enzyme activity responded to dilution in a linear mainner, thus permitting the prio adjustment of the milkclotting time as desired. The addition of calcium chloride increased the milk-clotting activity many folds up to 0.08:1T a3 final concentration, whereas the incorporation of sodium chloride in the reaction mixture resulted in significant inhibition of the clotting reaction particularly at high concentrations. The enzyme was heat-tolerant up to 60. On the other hand, the milk-clotting reaction catalyzed by this enzyme had an optimum temperature range between 70§ to 80§, thus, suggesting, possible activity protection by the presence of the substrate. The results obtained are discussed in the light of the application feasibility of this eyzyme as a substitute for animal rennet

Physiology and kinetics of a new L-Asparaginase from arthrobacter citreus

active intracellular L-asparagnase was detected in cultures of Arthrobacter citreus. The enzyme was farmed constitutively on a variety of media irrespective to the presence of the substrate or other structurally-related compounds. Glucose severely suppressed the enzyme formation The study of the physiology of formation has revealed that this enzyme reaches the maximum level at the end of the exponential phase and the beginning of stationary phase of growth followed by a rapid decline of the enzyme level upon further aging of the culture. The enzyme, obtained from the cells by benzene extraction. exhibited optimum activity at pH 3 and had an apparent KM 1.6 x l0-2M with respect to L- asparagire substrate. A significant substrate - protective effect was noted against heat iractivation of the enzyme at least up to 70§. The enzyme showed high specificity for L- asparagire and L- glutaminc with little or no activity on other amides tested. Significant activation was noted for magnesium ion whereas ferrous exhibited strong inhibitory effect. The properties of this enzyme are discussed in the light of possible application in cancer therapy

Distribution and biosynthesis requirements for L-Asparaginase activities in bacteria and yeasts

Screening of 40 bacterial cultures, belonging to 16 genera and 24 yeasts, belonging to 10 genera, for levels of L-asparaginase activities was carried using a simple medium with L-asparagine asthe major carbon and nitrogen source. Among bacteria highestenzyme levels were noted for certain cultures of Erwinia, Arthrobacter and Serratia; whereas some species of Rlhodotorula, Debaryomyces and Schwanniomyces yielded the highest L-asparaginase activities among the yeast cultures tested. The use of cells stored frozen for a few days was necessary to obtain reliable information about the enzyme levels in the surveyed cultures. Physiological studies on selected cultures have revealed that the enzyme is inducible with L-asparagine and some structurally-related metabolites in Rhodvmruia rubra and Aerobacter aerogenes, whereas in several other cultures the enzyme is formed constitutively. Ammonium ion was a potent supressor of enzyme biosynthesis. Highest enzym levels were detected in cultures during the exponential and at the beginning of the stationary phases of growth whereas a wide variation in the enzyme stability was noted in different cultures upon extended incubation

Formation and properties of L-Glutaminase and L-Asparaginase activities in pichia polymorpha

An ascogenous yeast with high potentialities for L-glutaminase and L-asparaginase formation was isolated from Egyptian soils by the application of the method of enrichment culture. The organism, identified as pichia polymorpha, was obtained through the enrichment of the soil samples with a simple medium containing 0.5% L-glutamine as a major carbon and nitrogen source at low pH values. - The amidase activities were produced constitutively on a variety of media irrespective to the presence of their substrates in the growth medium. The assays of enzyme activity have revealed that optimum pH values for L-glutamine and L-asparagine hydrolysis are 6 and 6.7 respectively. The L-asparaginase activity of the cells were heat-stable at least up to 10 min at 600. The enzyme exhibited apparent km of 1.37 x 10[-2] M and 1.95 x 10[-2] M for L-asparagine and L-glutamine respectively. No metal requirements were detected for the amidase activities of the organism under study