• Korean Journal of Microbiology
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• v.29 no.2
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• pp.111-116
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• 1991

Rhizopus nigricans produces 11.alpha.-hydroxyprogesternoe with a unidentified byproduct, which is hardly separated. Results of chromatography, IR and NMR spectroscopy identified the byproduct to be 11.alpha.-hydroxy-allopregnane-3,20-dione. R. nigricans was found to transform progesternoe into a monoform intermediate, 11.alpha.-hydroxyprogesterone, from which 11.alpha.-hydroxy-allopregnane-3,20-dione and 6.betha., 11.alpha. - dihydroxyprogesterone were formed respectively by 5.alpha.-reduction and 6.betha.-hydroxylation.

• Korean Journal of Microbiology
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• v.31 no.4
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• pp.306-311
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• 1993

The effects of methanol. used as a solvent for the hydrophobic substrate progesterone. on the morphology of Rhizopus nigricans and 11$\alpha$-hydroxylation of progesterone was investigated. The methanol tolerance of the 11$\alpha$-hydroxylase system in polyacrylamide immobilized R. nigricans mycelia as well as in free mycelia has been induced by adding various unsaturated fatty acids. biotin and ions into the cultivation medium. Immobilization of the cell seemed to protect the cells from denaturation by methanol. It gave higher reaction rate of progesterone than the free mycelia in the presence of methanol.500 $\mu$g/l of biotin was found to be the most effective induction agent for the methanol tolerance among tested chemicals. R. nixricans cells sustained its enzymatic activity at higher methanol concentrations as a result of accumulation of unsaturated fatty acids. especially oleic acid. in the membrane phospholipid.

• Mycobiology
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• v.28 no.4
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• pp.177-179
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• 2000

A soft rot of fruits caused by Rhizopus nigricans occurred on peach (Prunus persica var. vulgaris) in The Chinju City Agricultural Products Wholesale Marke during in summer season of 2000. The disease infection usually started from wounding after harvest fruits, and then moved to outside. At first, the lesions started with water soaked and rapidly softened and diseased area gradually expanded. In severely infected film house, the rate of infected fruits reached 65.2%. Numerous sporangiospores were produced on the diseased fruits. Most of the sporangiospores were appeared to be readily dispersed in the air. The mycelia grew surface of fruits and produced stolons. Colonies on potato dextrose agar at $25{\sim}30^{\circ}C$ white cottony at first becoming heavily speckled by the presence of sporangia and the browinish black at maturity, spreading rapidly by means of stolons fired at various points to the substrate by rhizoids. Sporangia were $85.3{\sim}243.5{\times}53.4{\sim}219.2\;{\mu}m$ in size and were globose or sub-globose with. somewhat flattened base. The color of sporangia was white at first and then turned black with many spores, and never over-hanging. Sporangiophores were $8.9{\sim}36.6\;{\mu}m$ in width, smooth-walled, non-septate, light brown, simple, long, arising in groups of $3{\sim}5$ from stolons opposite rhizoids. Sporangiospores was $9.7{\sim}24.8{\times}5.9{\sim}15.8\;{\mu}m$, irregular, round, oval, elongate, angular, and browinish-black streaked. Columella was $70.2{\times}149.7{\mu}m$. brownish gray, and umberella-shaped when dehisced. The causal organism was identified as. Rhizopus nigricans Lind on the basis of the morphiogical characteristics of the fungus. Rhizopus soft rot on peach (Prunus persica) caused by the fungi has not been reported in Korea. This is the first report of rhizopus soft rot on peach caused by Rhizopus nigricans in Korea.

• The Korean Journal of Mycology
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• v.18 no.2
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• pp.84-88
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• 1990

Hydroxylation in the $11{\alpha}$-position of progesterone molecules was carried out using Rhizopus nigricans spores immobilized within various gel matrices, among which polyacrylamide and agar gel were proved to be the most effective. Reactions with the immobilized cells and in­tact free cells showed almost identical conversion rate of progesterone, optimal pH and reaction time for attaining maximal yield, from which were confirmed absence of any decay and modification of enzyme activities.

• Mycobiology
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• v.47 no.3
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• pp.301-307
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• 2019

The $11{\alpha}$-hydroxylation of $16{\alpha}$, 17-epoxyprogesterone (EP) catalyzed by Rhizopus nigricans is crucial for the steroid industry. However, lower conversion rate of the biohydroxylation restricts its potential industrial application. The $11{\alpha}$-steroid hydroxylase CYP509C12 from R. oryzae were reported to play a crucial role in the $11{\alpha}$-hydroxylation in recombinant fission yeast. In the present study, the CYP509C12 of R. oryzae (RoCYP) was introduced into R. nigricans using the liposome-mediated mycelial transformation. Heterologous expression of RoCYP resulted in increased fungal growth and improved intracellular reactive oxygen species content in R. nigricans. The $H_2O_2$ levels in RoCYP transformants were approximately 2-folder that of the R. nigricans wild type (RnWT) strain, with the superoxide dismutase activities increased approximately 45% and catalase activities decreased approximately 68%. Furthermore, the $11{\alpha}$-hydroxylation rates of EP in RoCYP transformants (C4, C6 and C9) were 39.7%, 38.3% and 38.7%, which were 12.1%, 8.2% and 9.4% higher than the rate of the RnWT strain, respectively. This paper investigated the effect of heterologous expression of RoCYP in R. nigricans, providing an effective genetic method to construct the engineered strains for steroid industry.

• The Korean Journal of Mycology
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• v.21 no.3
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• pp.230-234
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• 1993

In order to isolate mutants in Rhizopus nigricans, the optimal treatment conditions for the chemical mutagens, N-Methyl-N'-Nitro-N-Nitrosoguanidine(MNNG) and Ethyl Methane Sulphonate(EMS), were explored. When MNNG was used as the chemical mutagen, the optimum concentration and treatment time for the best mutation frequency were $125{\mu}g/ml$ and 60 minutes, respectively. Under the optimum conditions for MNNG, the survival rate was 0.1-1.0%. The leucine auxotroph could be isolated. The phenotypic characteristics of the three mutants prepared are as follows; shortened sporangiophore, spiral sporangiophore, and reduced size of sporangium and sporangiospore. However, EMS as the chemical mutagen was ineffective for this species.

• The Korean Journal of Mycology
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• v.22 no.2
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• pp.138-144
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• 1994

Conditions for isolation of protoplasts from spores and mycelia of Rhizopus nigricans were studied. Larger amount of protoplasts was obtained from swollen spores in liquid medium contained with 5% of 2-deoxy-D-glucose for 4 hours than from mycelia. Enzyme mixture of Novozym 234(2%) and ${\beta}-glucuronidase(5000\;unit/ml)$ was most effective for the isolation of protoplasts from swollen spores and from mycelia. The solution of 0.6 M $MgSO_4$ or mannitol and pH 6.0 showed good results as the osmotic stabilizer and the optimal condition of pH of the enzyme solution for the isolation of protoplast from the swollen spores, respectively. At this condition, $8.0{\times}10^6\;cells/ml$ of protoplasts was obtained from swollen spores by digestion with lytic enzyme mixture for 2 hours.

• Microbiology and Biotechnology Letters
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• v.18 no.1
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• pp.66-70
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• 1990

A study on 11 $\alpha$-hydroxylation of progesterone by using Rhizopus nigricans was carried out to produce efficiently 11 $\alpha$-hydroxyprogesterone which is an essential intermediate of corticosteroids synthesis. Firstly, medium was optimized in view of bioconversion yield and cell growth. Glucose and casamino acid were selected as carbon and nitrogen source and the ratio of carbon to nitrogen which maximize bioconversion yield was determined to be 2:1. Secondly, the addition time of progesterone and dispersion method were studied. When progesterone dispersed with 0.01% (v/v) Tween 80 was added at 12-14 hr of cultivation, higher bioconversion yield was obtained. When 20g/$\ell$ of progesterone was added, the yield reached 70% under optimized conditions.

• Korean Journal of Microbiology
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• v.20 no.3
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• pp.134-146
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• 1982

This experiment was designed to elucidate the life cycle of 7 species (Rh.nigricans, Rh. delemar, Rh.oryzae, Rh.acidus, Rh.tritici, Rh. formosaensis and Rh. japonicus) in genus Rhizopus isolated from Korean soil, so as to seize the appropriate stage for detecting their chromosomal number and nuclear size under the method of thin layer slide culture using modified Rogers(1965a) medium. The results are summarized as the folowings ; 1. The haploid chromosome number are found 16 in Rh. japonicus are 8, respectively. 2. Comparing the 7 species of Rhizopus with each other, it may be concluded that the basic haploid chromosome number of genus Rhizopus distributed in Korean soil are 8 and that Rh. nigricans is double of the basic hapolid chromosome number (n = 16). Besides them, the other two species (Rh. tritici and Rh. formosaensis) are believed aneuploids.

• The Korean Journal of Mycology
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• v.15 no.1
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• pp.23-28
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• 1987

Physicochemical factors influencing the $11{\alpha}$, hydroxylation of progesterone by Rhizopus nigricans Ehrenberg were studied. The higher is the concentration of progesterone. the shorter time is need to attain maximum yield in the $11{\alpha}-hydroxyprogesterone$. High concentration in progesterone was supposed to inhibit the hydroxylation reaction of the $11{\alpha}-hydroxyprogesterone$. The range of optimum pH and temperature appeared to be rather broad and these conditions were similar to those of optimum growth of the mycelia. Agitation at a higher speed than a certain limit, and the presence of sugars accelerated the $11{\alpha}-hydroxyprogesterone$ reaction. Glucose was found to be more effective for the reaction using spores rather than mycelia as enzyme sources. Organic solvents were proved to supress the enzyme activity, which decreased with increase in the concentration of the organic solvents and in the time for pretreatment with the solvents.