[Show abstract][Hide abstract] ABSTRACT: Poly(hydroxybutyric acid) (PHB) and other biodegradable polyesters are promising candidates for the development of environment-friendly, totally biodegradable plastics. The use of cane molasses and corn steep liquor, two of the cheapest substrates available in Egypt, may help to reduce the cost of producing such biopolyesters. In this work, the effect of different carbon sources was studied. Maximum production of PHB was obtained with cane molasses and glucose as sole carbon sources (40.8, 39.9 per mg cell dry matter, respectively). The best growth was obtained with 3% molasses, while maximum yield of PHB (46.2% per mg cell dry matter) was obtained with 2% molasses. Corn steep liquor was the best nitrogen source for PHB synthesis (32.7 mg per cell dry matter), on the other hand, best growth was observed when ammonium chloride, ammonium sulphate, ammonium oxalate or ammonium phosphate were used as nitrogen sources.
Microbiological Research 02/2001; 156(3):201-7. · 1.99 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Acetone fractionation of Bacillus lentus culture filtrate yielded the highest -amylase activity and the 66.6% fraction reached 13-fold that of the crude enzyme preparation. Gel filtration and ion exchange chromatography afforded a pure -amylase (relative molecular mass, 42 000). The pure enzyme was highly active on starch and dextrin. It produced a mixture of oligosaccharides as major products of starch hydrolysis. Maximal activity was reached at 70 C and pH 6.1. Ca2+, Na+, K+ and Sr2+ ions stabilized or slightly stimulated the enzyme whereas Ag+, Co2+, Hg2+, Zn2+, Cd2+ and Fe3+ ions strongly inhibited the activity. The enzyme contained 16 amino acids, of which aspartic and glutamic acids were present in the highest proportions.
Applied Microbiology and Biotechnology 11/1992; 38(3):312-314. · 3.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The formation of citric acid, oxalic acid, erythritol and glycerol by three strains of Aspergillus niger immobilized in calcium alginate was investigated and compared with that of free cells when cultivated in shake flasks under phosphate limitation. Morphological changes were followed using an electron microscope. The production of acids and polyols, the consumption of glucose and fructose, and also the morphological changes were strain-dependent. The results also reflected the influence of long storage of a strain on productivity, morphological behaviour and phosphate consumption.
Applied Microbiology and Biotechnology 12/1991; 36(4):518-524. · 3.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The degradation rate of hydrocarbons in oily sludge obtained from a flotation unit by free and immobilized cells in shaking flasks and in a stirred tank reactor was investigated. For the biodegration of 3.3% hydrocarbons free cells and cells immobilized on granular clay were used. Free cells needed 7–8 weeks to use 30% of the 3.3% hydrocarbons, whereas with immobilized cells the same result was obtained after 3–4 weeks only. In shaken flasks with high hydrocarbon concentrations (8%), immobilized Candida parapsilosis degraded 90% of the hydrocarbons in the oily sludge within 3 weeks, while free cells degraded only 27.5% in the same period. In degradation experiments with a bioreactor, free and immobilized cells of the isolate ISO-OS B 20 showed better results compared to cultures in shaken flasks due to better aeration and mixing. Free cells degraded 50% of the 5% hydrocarbon-containing oily sludge in 7 weeks, whereas immobilized cells gave the same result after only 4 weeks.
Applied Microbiology and Biotechnology 10/1990; 34(2):259-263. · 3.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Living cells of Candida parapsilosis KSh 21 were immobilized by adsorption on different types of glass rings. The presence of n-tetradecane enhanced the cell adsorption especially on normal glass rings. The high adhesion of cellulose-coated glass rings and of sintered glass rings induced a quick adsorption of the cells. The quantity of 1-tetradecanol produced in the cultures of immobilized cells especially on SGR was higher than that of the free cells. Low numbers of free cells released in the immobilized cultures were observed. Better contact between the immobilized cells and oil droplets was noticed.
Applied Microbiology and Biotechnology 10/1988; 29(5):442-446. · 3.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The immobilization intensity of cells of Penicillium frequentans and Candida parapsilosis on materials such as granular clay, granular clay + aquifer sand and aquifer sand alone, was followed by scanning electron microscopy (SEM). The results demonstrate that the granular clay was the best adsorbent for both organisms, followed by the mixture of both granular clay and aquifer sand. Poor adhesion of cells was detected on using aquifer sand alone with C. parapsilosis.The highest degree of degradation of the alkane mixture (C12–C18) used was achieved by cells immobilized on granular clay, followed by those cells adsorbed on clay and sand. The weakest degradation was observed with cells immobilized on the sand alone.
Applied Microbiology and Biotechnology 02/1988; 28(1):103-108. · 3.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The activity of enzymes of the tricarboxylic acid (TAC) and glyoxylate (GC) cycles in Candida parapsilosis (wild type KSh 21 and mutant 337) were studied under different physiological and metabolic conditions.
C. parapsilosis differed in most of its enzyme activities from other non-citric acid producing yeasts. Furthermore, pH-value, temperature and age of culture proved to act differently on both strains of the tested organism.The addition of trans-aconitate increased not only the growth but also the activities of citrate synthase and some other enzymes while that of aconitase decreased enormously.The high citrate synthase activity might be connected with the role of citrate in the transport of acetyl groups.
Applied Microbiology and Biotechnology 02/1980; 11(1):35-41. · 3.69 Impact Factor