ABSTRACT
In this study, the production of enantiopure benzoin from rac-benzoin acetate was achieved by lipase catalyzed kinetic resolution combined with deracemization using Rhizopus oryzae (CBS111718). The growth cells were pretreated with 20 kHz and 30 kHz ultrasound irradiation and mechanical homogenization. Approximately 100% conversion and 96% enantiomeric excess of the product (S-benzoin) were obtained by applying 20 kHz ultrasound irradiation at pH 6. The deracemization process involves new and important processes that allow for the transformation of a racemate into a single stereoisomeric product in 100% theoretical yields. Moreover, the application of ultrasound increases the conversion rate by reducing mass transfer limitation.
Subject(s)
Benzoin/chemical synthesis , Lipase/metabolism , Plant Proteins/metabolism , Racemases and Epimerases/metabolism , Rhizopus/radiation effects , Acetates/chemistry , Catalysis/radiation effects , Hydrolysis/drug effects , Hydrolysis/radiation effects , Isomerism , Kinetics , Radio Waves , Rhizopus/enzymology , StereoisomerismABSTRACT
Low-energy ion beam irradiation (10-200 keV) has been proved to have a wide range of biological effects in recent years. When Rhizopus oryzae PW352 was irradiated with a 15-keV low-energy ion beam an L(+)-lactic acid high-yield mutant, RQ4015, was obtained. When 150 g/l glucose was used as the sole carbon source, L(+)-lactic acid of RQ4015 reached 121 g/l after 36 h shake-flask cultivation. However, the highest lactic acid concentration 74 g/l was obtained when 100 g/l xylose was present in the medium as the sole carbon source. When mixed xylose (25 g/l) and glucose (75 g/l) were present in a bubble column, L(+)-lactic acid production of RQ4015 reached 83 g. A high mutation rate and a wide mutation spectrum of low-energy ion implantation were observed in the experiment, suggesting that ion implantation can be a highly efficient mutagenic means for microorganism breeding in many commercial applications.
Subject(s)
Glucose/metabolism , Lactic Acid/biosynthesis , Rhizopus/metabolism , Rhizopus/radiation effects , Xylose/metabolism , Fermentation , Mutation , Rhizopus/geneticsABSTRACT
Spores from the co-culture of Aspergillus foetidus and Rhizopus oryzae were subjected to UV, heat and NTG (3-nitro,5-methylguanidine) mutagenesis. A few colonies were screened from the selected media for tannase study. Amongst all, the best mutant isolated from the heat treatment (60 degrees C for 60 min) was SCPR 337. The maximum yield of gallic acid and tannase in case of mutant strain was 95.2% and 53.6 U/ml with an incubation period of 30 h as compared to wild strain where the incubation period was 48 h with an enzyme activity of 44.2 U/ml and gallic acid yield of 94%, respectively. The mutant was sensitive to tetracycline and was also an over-producer of protease and amylase.
Subject(s)
Aspergillus/metabolism , Carboxylic Ester Hydrolases/biosynthesis , Industrial Microbiology/methods , Rhizopus/metabolism , Amylases/metabolism , Aspergillus/genetics , Aspergillus/growth & development , Aspergillus/radiation effects , Coculture Techniques , Enzymes/metabolism , Fermentation , Gallic Acid/metabolism , Methylnitronitrosoguanidine/pharmacology , Mutagenesis , Mutation , Rhizopus/genetics , Rhizopus/growth & development , Rhizopus/radiation effects , Tetracycline/pharmacology , Ultraviolet RaysABSTRACT
The production of L(+)-lactic acid and formation of gamma-linolenic acid by 50 Rhizopus strains growing on saccharidic substrates were investigated. Formation of acids was observed on solid cultivation media but mainly during submerged fermentation. Strains with the highest selectivity of both L(+)-lactic acid production and gamma-linolenic acid formation were tested in a laboratory fermenter. The best producer was treated by UV irradiation to increase the fatty acid content in the biomass, especially that of gamma-linolenic acid. The conversion of 10% saccharidic substrate by this newly prepared strain Rhizopus arrhizus CCM 8109 results in more than 95% of theoretical yield of L(+)-lactic acid and permits a volume productivity of 0.4 g gamma-linolenic acid per liter.
Subject(s)
Lactates/biosynthesis , Linolenic Acids/biosynthesis , Rhizopus/metabolism , Biotechnology , Culture Media , Fermentation , Lactic Acid , Mycology/methods , Rhizopus/growth & development , Rhizopus/radiation effects , gamma-Linolenic AcidABSTRACT
The most effective way for inducing mutants of Rhizopus microsporus with an elevated lipolytic activity is the combined action of nitrosomethyl urea and UV. Variants with the lipolytic activity of 3600--3700 units per 1 ml have been produced, thus being by 72--75% more effective than the parent culture.
Subject(s)
Lipase/biosynthesis , Rhizopus/enzymology , Dose-Response Relationship, Drug , Lipase/genetics , Methylnitrosourea/pharmacology , Mutation , Rhizopus/drug effects , Rhizopus/radiation effects , Ultraviolet RaysABSTRACT
The high occurrence of Alternaria humicola and the moderate occurrence of Stemphylium verruculosum, Rhizopus nigricans, and Epicoccum nigrum in the air of Egypt could be correlated to their apparent resistance to solar radiation. Cladosporium herbarum, Aspergillus niger, and Penicillium oxalicum, although highly occurring, were light-sensitive. The miniumum solar radiation in November, coupled with the highest total fungal catch, dominated by Cladosporium herbarum, reveals the importance of solar radiation as a factor with direct effect on the air fungal population.
