The yeast
Pichia guilliermondii was examined for its ability to control
Rhizopus nigricans on tomato fruit during storage, and in order to highlight the reason for biocontrol, a possible mode of ...action is discussed. Results showed that autoclaved yeast culture and culture filtrate had no effect on controlling the postharvest disease caused by
R. nigricans, although inoculation of
P. guilliermondii prior to
R. nigricans resulted in enhanced biocontrol efficacy. Moreover, rapid colonization of the yeast on wound sites was observed during the initial 3 days at 20
°C, and then the population stabilized for the remaining 4 days. This phenomenon indicated that at room temperature,
P. guilliermondii could acclimatize itself to the environment of tomato fruit wounds and occupy the living space quickly. The results indicate that
P. guilliermondii did not produce an antifungal substance, however, competition for nutrients and space on wounds appeared to play a role in the activity of the biocontrol and could be one of the mechanisms. In addition, the fruit inoculated with
P. guilliermondii demonstrated changes in peroxidase (POD), polyphenoloxidase (PPO), superoxide dismutase (SOD), catalase (CAT), phenylalanine ammonia-lyase (PAL), chitinase (CHI) and β-1,3-glucanase activities, all of which were correlated with the onset of induced resistance. This result suggests that tomato fruit is capable of responding to the yeast
P. guilliermondii, which could activate defensive enzymes and thereby induce host disease resistance.
Cytochrome P450 monooxygenases are a unique family of enzymes that are able to catalyze regio- and stereospecific oxidations for a broad substrate range. However, their highly-effective industrial ...application is often limited by the regeneration of cofactor NADPH. In this study, G6PDH from Rhizopus oryzae was expressed to enhance the regeneration of NADPH in the industrial strain, R. nigricans. The results showed the fermentation time of the engineered strain was shortened to 52h when the hydroxylation yields reached the maximum, which was 4h ahead compared to that of the original strain. 95.4%-higher-level NADPH could be generated and the hydroxylation yield increased by 15.6% in an engineered strain after 52-h fermentation compared to those in the original strain after 56-h fermentation. The results indicated that the strategy of enhancing NADPH regeneration by expressing G6PDH was simple and effective on improving the P450-monooxygenase-dependent hydroxylation ability in filamentous fungi.
Extracellular polysaccharide (EPS1-1) was obtained from Rhizopus nigricans and its structural features have been measured. The purpose of this study was to investigate the anti-inflammation effect of ...EPS1-1 on the chronic atrophic gastritis induced by N-methyl-n'-nitro-n-nitrosoguanidine (MNNG). EPS1-1 could decrease the damage of MNNG including the increased hemorrhagic spots, disorganized glands of gastric mucosa and marked inflammatory cell infiltration. Furthermore, compared to the model group, EPS1-1 treatment could down-regulate the level of inflammation-associated genes and up-regulate the expression of immune-related genes with the analysis of a gene expression profile. Besides, EPS1-1 was found to significantly enhance the immunity of mice. The thymus index of the EPS1-1 group increased significantly compared with that of the model group, and the serum creatinine and blood urea nitrogen levels of kidney and liver decreased in the EPS1-1 group. These studies showed that EPS1-1 may be a beneficial ingredient for improving gastrointestinal health.
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•EPS1-1 reduced the damage caused by MNNG to gastric mucosa and inhibits the occurrence of chronic atrophic gastritis.•EPS1-1 protected the function organs such as liver and kidney and improves immunity in mice.•The extraction process of EPS1-1 is simple with high purity and EPS1-1 has a good potential to be used in functional foods.
This study reports the biosorption of Cr(VI) by chemically modified biomass of Rhizopus nigricans and the possible mechanism of Cr complexation to the adsorbent. The cell wall of this fungus ...possesses strong complexing property to effectively remove Cr(VI) anions from solution and wastewater. The mechanism of Cr adsorption by R. nigricans was ascertained by chemical modifications of the dead biomass followed by FTIR spectroscopic analysis of the cell wall constituents. Treatment of the biosorbent with mild alkalies (0.01N NaOH and ammonia solution) and formaldehyde (10%, w/v) deteriorated the biosorption efficiency. However, extraction of the biomass powder in acids (0.1N HCl and H2SO4), alcohols (50% v/v, CH3OH and C2H5OH) and acetone (50%, v/v) improved the Cr uptake capacity. Reaction of the cell wall amino groups with acetic anhydride reduced the biosorption potential drastically. Blocking of the –COOH groups by treatment with water soluble carbodiimide also resulted in initial lag in Cr binding. Biomass modification experiments conducted using Cetyl Trimethyl Ammonium Bromide (CTAB), Polyethylenimine (PEI), and Amino Propyl Trimethoxy Silane (APTS) improved the biosorption efficiency to exceptionally high levels. The FTIR spectroscopic analysis of the native, Cr bound and the other types of chemically modified biomass indicated the involvement of amino groups of Rhizopus cell wall in Cr binding. The adsorption data of the native and the most effectively modified biomass were evaluated by the Freundlich and the Langmuir adsorption isotherms and the possible adsorption phenomena are also discussed.
ABSTRACT
In this article, in vitro and in vivo antifungal activities of clove oil to inactivate Aspergillus flavus, Penicillium citrinum and Rhizopus nigricans were investigated. The result showed ...that eugenol (approximately 83.02%) is the main constituent of clove oil. The minimum inhibitory concentrations of clove oil against A. flavus, P. citrinum and R. nigricans were 25, 25 and 50 µL/mL, respectively. In an in vitro experiment, the results revealed that clove oil possessed stronger antifungal activities against A. flavus and P. citrinum than against R. nigricans, and the antifungal activity improved with increasing its concentration. In an in vivo study, clove oil treatments significantly reduced fungal decay, and clove oil at a concentration of 3.0% showed complete control of A. flavus and P. citrinum in wound‐inoculated fruit. These results indicated that clove oil has a good potential to be a natural antifungal agent for fruit applications.
PRACTICAL APPLICATIONS
Postharvest decay caused by fungi is the major cause of rapid deterioration of fruits, which affects the quality and shortens the shelf life of fruits and vegetables. The major problems for the application of chemical preservatives are the increasing resistance to antibiotics and chemotherapeutics and health risk concerns. So, most consumers demand less use of synthetic additives to ensure food safety. There is a growing need to develop alternative approaches, such as the application of essential oils, for controlling postharvest diseases.
11alpha-Hydroxylation of 16alpha,17-epoxyprogesterone (EP) by Rhizopus nigricans is an essential step in the synthesis of many steroidal drugs, while low conversion of the biohydroxylation is a tough ...problem to be solved urgently in industry. Two ionic liquids (ILs) of BMImPF sub(6) and BMImNTf sub(2) were used in the biotransformation of EP by R. nigricans. The results indicated that the conversion carried out in BMImPF sub(6)-aqueous biphasic system was greatly increased to above 90% at 18 g/L feeding concentration. A simplified mechanism was proposed to explain the improvement of the bioconversion in a biphasic ionic liquid aqueous system. Besides, successive three batches of bioconversion were carried out in the biphasic system with a total conversion of 87% at phase ratio 10 and 75% at phase ratio 5, respectively. Since recycling of the BMImPF sub(6) is quite easy, there is a great potential for the application of ILs in fungi biotransformation to implement green production.
Plants are endowed with a sophisticated defense mechanism that gives signals to plant cells about the immediate danger from surroundings and protects them from pathogen invasion. In the search for ...the particular proteins involved in fruit defense responses, we report here a comparative analysis of tomato fruit (Solanum lycopersicum cv. Ailsa Craig) infected by Rhizopus nigricans Ehrenb, which is a significant contributor to postharvest rot disease in fresh tomato fruits. In total, four hundred forty-five tomato proteins were detected in common between the non-infected group and infected tomato fruit of mature green. Forty-nine differentially expressed spots in 2-D gels were identified, and were sorted into fifteen functional groups. Most of these proteins participate directly in the stress response process, while others were found to be involved in several equally important biological processes: protein metabolic process, carbohydrate metabolic process, ethylene biosynthesis, and cell death and so on. These responses occur in different cellular components, both intra- and extracellular spaces. The differentially expressed proteins were integrated into several pathways to show the regulation style existing in tomato fruit host. The composition of the collected proteins populations and the putative functions of the identified proteins argue for their roles in pathogen-plant interactions. Collectively results provide evidence that several regulatory pathways contribute to the resistance of tomato fruit to pathogen.
Previous studies have shown that some stressors, including steroid hormones 21-OH progesterone and testosterone, stimulate the accumulation of heat shock protein 70 (hsp70 ) messenger ribonucleic ...acid (mRNA) population in the zygomycete filamentous fungus Rhizopus nigricans. In this study we report the cloning of 3 R nigricans hsp70 genes (Rnhsp70-1, Rnhsp70-2, and Rnhsp70-3 ) encoding cytosolic Hsp70s. With a Southern blot experiment under high stringency conditions we did not detect any additional highly homologous copies of the cytosolic hsp70 genes in the R nigricans genome. Sequence analyses showed that all 3 genes contain introns within the open reading frame. The dynamics of the R nigricans molecular response to progesterone, 21-OH progesterone, and testosterone, as well as to heat shock, copper ions, hydrogen peroxide, and ethanol was studied by temporal analysis of Rnhsp70-1 and Rnhsp70-2 mRNA accumulation. Northern blot experiments revealed that the Rnhsp70-2 transcript level is not affected by testosterone, whereas mRNA levels of both genes are rapidly increased with all the other stressors studied. Moreover, the decrease of transcript levels is notably delayed in ethanol stress, and a difference is observed between the profiles of Rnhsp70-1 and Rnhsp70-2 transcripts during heat stress.
•The external (ECA) and internal (ICA) area of saffron corm were lyophilized and sterilized to prepare agar plates.•ECA showed the highest inhibitory effects against the five isolated fungi from ...infected corms during August.•The saponin fraction exclusively detected on ECA, is partially responsible for its extra effect.•The main inhibitory effect of these saponins was against Fusarium oxysporum followed by Bipolaris spicifera and Aspergillus niger.•The inhibitory effect against Penicillium raistriicki and Rhizopus nigricans was almost negligent.
Fungi cause important deteriorations of corms from Crocus sativus L. In order to screen the antifungal properties of this organ to fight such infections, two independent experiments based on the lyophilized and sterilized external (peel) and internal parts of the corm were conducted against five fungi isolated from infected corms during August. The minimum inhibitory concentrations (MIC) after 30 days of the peel treatments were 5.4% against Aspergillus niger, 3.9% against Bipolaris spicifera, Fusarium oxysporum, Penicillium raistriicki and 2.3% against Rhizopus nigricans while the MIC of the internal part were not detected for A. niger and B. spicifera, 7.0% against F. oxysporum and P. raistriicki and 3.9% against R. nigricans. The higher toxicity of the peel against fungi led us to investigate the influence of the saponins exclusively detected on the external part of the corm, as partially responsible for the extra observed effect. The main influence of these compounds on the toxicity was against F. oxysporum, the most desvasting pathogen in saffron corms, followed by B. spicifera and A. niger. The growth inhibition of P. raistriicki and R. nigricans was almost negligible. However, other compounds such as phenolics compounds could also be responsible for the fungicidal activity detected. These results illustrate that saffron corms could be further exploited in order to discover new phytochemical products with antifungal properties.
Results of an integrated approach for the improvement of progesterone 11α-hydroxylation by
Rhizopus nigricans, which is one of the key steps in the production of corticosteroid drugs and hormones, ...are presented. Several issues have been addressed in order to increase process productivity, including biocatalyst immobilization, improvement in the solubility of the lipophilic substrate, setting-up of continuous reaction process and easing downstream processing. After preliminary studies on the effects on
Rhizopus nigricans morphology, fungal pellets of a desired size and structure could be obtained. The mycelia grown in spherical agglomerates further enabled its continuous use in the process of biotransformation. The problem of low steroid solubility was addressed by the addition of organic solvents or β-cyclodextrin. In order to develop an integrated biotransformation process, a continuous two-liquid phase extraction within microchannel device has been set up, where very efficient steroid extraction was achieved within a few seconds.
![11[alpha]-Hydroxylation of ...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0960-8524/small "11[alpha]-Hydroxylation of 16[alpha],17-epoxyprogesterone by Rhizopus nigricans in a biphasic ionic liquid aqueous system")
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