Mucor Strains Research Articles

Clinical Trial to Evaluate Safety and Efficacy of Thinqure20 (A Herbal Composition) in the Treatment and Prophylaxis of Novel Coronavirus and Testing its In vitro- Potential against MS2 Bacteriophagae, Corona Virus, Influenza Virus and Mucor racemosus

Background and Objective: Thinqure20 is a polyherbal, reverse-pharmacology-based formulation that contains Piper longum, Piper nigrum, Zingiber officinale, and rock salt as active ingredients. It is designed to work as an effective antiviral agent and also as a preventive measure against SARS-CoV-2. Clinical and non-clinical studies have established significant safety efficacy and tolerability of Thinqure20 formulation in the treatment of COVID-19 infection. Methods: In vivo human study was conducted on COVID-19 patients for 5 days. A total of 30 Covid-19 patients (n = 30) were enrolled. In vitro, cell line studies were also carried out to evaluate the potential effectiveness of Thinqure20 polyherbal formulation as an antiviral, antifungal, and Angiotensin- Converting Enzyme 2 (ACE2) inhibition. Results: Human studies have demonstrated a mean percentage of reduction in viral load from baseline to end of the study visit which was found to be 75.4%. The minimum and maximum reduction in viral load was found to be 59.3% and 100%, respectively. Viral load testing was carried out by Reverse Transcriptase-quantitative Polymerase Chain Reaction (RT-qPCR) test. In vitro studies of Thinqure, 20 extracts showed potential antiviral activity against MS2 bacteriophage, influenza, and human coronavirus, antifungal activity against Mucor racemosus, and significant ACE2 receptor inhibition. Conclusion: Thinqure20, a polyherbal formulation, is a potentially effective antiviral agent against non-enveloped viruses (MS2 bacteriophage), enveloped viruses (influenza and human coronavirus), and antifungal agent against mucor strains. It is also proven to be effective in the treatment of COVID-19 and can be attributed to an early recovery by the reduction in viral load. Clinical Trail Registration Number: CTRI/2021/03/032471.

Antifungal Activity of a Wireless Electroceutical Dressing

Background:Fusarium and Mucor are two filamentous fungus strains that can cause infections in humans. Fusarium is known for causing corneal infections. Patients who have diabetes mellitus or are immunocompromised are at a higher risk of mucormycosis. Wireless electroceutical dressing (WED) contains embedded silver and zinc nanoparticles in a geometric pattern. Both zinc and silver have been known to be antimicrobial; yet the combination results in a weak electric field when exposed to an electrolyte-containing solution. WED has been found to have antifungal effects against Candida albicans and Aspergillus fumigatus.
 Methods:We investigated the antifungal effect of WED against Fusarium and Mucor growth and survival through daily radial growth and optic density readings.
 Results:Our results show that the WED weakly inhibits radial growth of Fusarium strains and strongly inhibits radial growth of Mucor strains, with greater inhibition near physiologic temperatures. Although zinc and silver-only fabric inhibited the radial growth of Mucor, no growth occurred on WED (Ag-Zn) plates for Mucor strains. Optic density readings had mixed results; Ag-Zn liquid cultures had reduced absorbance than control cultures for both strains. Zone of inhibition studies of Fusarium showed no growth on Ag-Zn fabrics with full coverage on all other control and metal containing plates. WED had a greater effect on reducing Mucor growth than Fusarium.
 Conclusions:WED utilizes a weak electrical field created by silver and zinc nanoparticles to create an antifungal effect. This leads to strong inhibition of Mucor, Candida, and Aspergillus growth and weak inhibition of Fusarium growth. Further studies are needed to determine the specific effect of WED on fungal viability, the mechanism, and in vivo efficacy. This work could increase patient treatment options for fungal wound infections.

Identification of Previously Unrecorded Bacills, Serratia, and Mucor Strains Isolated from Yogurt

(1) Background: Foodborne illnesses are recognized as a significant threat to public health and the economy in both developed and developing nations. The safety of foods containing microorganisms has consequently become a major worldwide concern. One of the most frequent causes of food deterioration in the world is microbial contamination. (2) Methods: Yogurt containers that were bought commercially in Riyadh, Saudi Arabia during their validity period contained four different species of bacteria and one type of fungus. Using nutritional agar and Czapek-Dox agar medium, the bacteria and fungi were isolated. The isolates of the fungi and bacteria were identified using a scanning microscope. The isolates were further identified and classified for molecular evolutionary analyses using the 16S rRNA and ITS sequences from the bacteria and fungi, respectively, in conjunction with the universal primers 27F, 1492R, ITS1F, and ITS4R. (3) Results: A total of 131 separate strains were identified from 12 yogurt samples based on their phenotypic characteristics. In total, 79 isolates (60.3%) consisted of Serratia marcescens, Bacillus subtilis, and Mucor circinelloides, with 52 isolates (39.7%) being Bacillus cereus. While the cells of Bacillus and Serratia are shaped like rods, the sporangia of Mucor are large, round, and black. Each strain was identified by its accession number, which were as follows: MK590996.1: B. cereus; MK591144.1: B. subtilis; MK591002.1 and MK591014.1: S. marcescens; and MK559692.1: M. circinelloides. The maximum identification was found to be between 98.64 and 100% when BLAST was used to compare the sequences to the NCBI GeneBank database. (4) Conclusions: Genus and species identification was performed using the similarity score values. Yogurt products containing high concentrations (39.7%) of Bacillus cereus isolates carry a significant risk of health hazards due to the potential for spreading pathogenic bacteria to humans.

Mucor tofus, a new species isolated from Mao-tofu (a fermented soybean food) in China

During studies on the diversity of Mucorales associated with traditional fermentation food from China, two Mucor strains were isolated from the surface of Mao-tofu, a fermented soybean food. Phylogenetic analyses of the internal transcribed spacer (ITS) and the large subunit (LSU) rDNA sequences revealed that the new isolates belong to the M. mucedo group and are closely related to M. mucedo. However, they differ from other species of this group by producing swollen, tall sporangiophores, sporangia measuring 40–260 µm and irregular sporangiospores. The maximum growth temperature of the new isolates is 33 °C, which is higher than other species in the M. mucedo group. Based on the combination of morphological characteristics, growth experiments and molecular phylogenetics, a new species Mucor tofus is proposed. Detailed phylogenetic trees, descriptions and illustrations are provided.

Role of Cytosolic Malic Enzyme in Oleaginicity of High-Lipid-Producing Fungal Strain Mucor circinelloides WJ11.

Mucor circinelloides, an oleaginous filamentous fungus, is gaining popularity due to its ability to synthesize significant amounts of lipids containing γ-linolenic acid (GLA) that have important health benefits. Malic enzyme (ME), which serves as the main source of NADPH in some fungi, has been found to regulate lipid accumulation in oleaginous fungi. In the present study, the role of two cytosolic ME genes, cmalA and cmalB, in the lipid accumulation of the M. circinelloides high-lipid-producing strain WJ11, was evaluated. Strains overexpressing cmalA and cmalB showed a 9.8- and 6.4-fold rise in specific ME activity, respectively, and an elevation of the lipid content by 23.2% and 5.8%, respectively, suggesting that these genes are involved in lipid biosynthesis. Due to increased lipid accumulation, overall GLA content in biomass was observed to be elevated by 11.42% and 16.85% in cmalA and cmalB overexpressing strains, respectively. Our study gives an important insight into different studies exploring the role of the cmalA gene, while we have for the first time investigated the role of the cmalB gene in the M. circinelloides WJ11 strain.

Biosurfactant-Producing Mucor Strains: Selection, Screening, and Chemical Characterization

Biosurfactants are amphiphilic molecules with surface tension reducing activities. Among biosurfactant producers, fungi have been identified as promising organisms. While many studies have investigated biosurfactant production in fungal species from the Ascomycota and Basidiomycota phyla, less is known concerning species from the Mucoromycota phylum. In this context, the aim of this study was to screen and optimize biosurfactant production in 24 fungal strains, including seven Mucor, three Lichtheimia, and one Absidia species. After cultivation in a medium stimulating surfactant production, the surface activity of cell-free supernatants was measured using both oil spreading and parafilm M tests. Among them, five Mucor strain cell-free supernatants belonging to M. circinelloides, M. lanceolatus, M. mucedo, M. racemosus, and M. plumbeus, showed oil repulsion. Then, the impact of the medium composition on surfactant production was evaluated for eight strains. Three of them, i.e., Mucor circinelloides UBOCC-A-109190, Mucor plumbeus UBOCC-A-111133, and Mucor mucedo UBOCC-A-101353 showed an interesting surfactant production potential, reducing the medium surface tension to 36, 31, and 32 mN/m, respectively. A preliminary characterization of the surfactant molecules produced by these strains was performed and showed that these compounds belonged to the glycolipid family.

Effect of Zinc-Calcium on Xylose Consumption by Mucor circinelloides (MN128960): Xylitol and Ethanol Yield Optimization

Xylose is the second most abundant monomeric sugar on earth. Nevertheless, metabolizing xylose into ethanol is a complex process due to several biochemical reactions. Some microorganisms of the genus Mucor are suitable for this bioprocess. Using metal ions, such as zinc and calcium, allows some fungal species to increase their ethanol yield. In this work, the wild strain Mucor spp. (C1502) was molecularly identified via internal transcribed spacer (ITS) sequencing. Secondly, an optimization using response surface methodology (RSM) with a central composite experimental design (CCD) was carried out. The independent variables (X) were ZnSO4·7H2O (X1, 0.0–1.5 g/L) and CaCl2 (X2, 0.0–2.5 g/L) concentration in the fermentation broth in order to demonstrate the effect of these ions, xylose was used as the only carbon source. The dependent variables (Y) measured were ethanol yield (Y1, g ethanol/g xylose) and xylitol yield (Y2, g xylitol/g xylose). The identified strain, Mucor circinelloides, was given the accession number MN128960 by the NCBI. Once the optimal concentrations of zinc and calcium were calculated, experimental validation was performed, with the highest ethanol and xylitol yields reaching 0.36 g ethanol/g xylose and 0.35 g xylitol/g xylose, respectively. This study demonstrated that increasing the xylitol yield using the effect of the ions, zinc and calcium, increases the ethanol yield. Furthermore, M. circinelloides (C1502) can produce metabolites, such as ethanol and xylitol, from the xylose obtained from hemicellulose biomasses, which can be used as a carbon source at low cost and with great availability.

Characterization of Four Novel dsRNA Viruses Isolated from Mucor hiemalis Strains.

We previously screened the total nucleic acid extracts of 123 Mucor strains for the presence of dsRNA molecules without further molecular analyses. Here, we characterized five novel dsRNA genomes isolated from four different Mucor hiemalis strains with next-generation sequencing (NGS), namely Mucor hiemalis virus 1a (MhV1a) from WRL CN(M) 122; Mucor hiemalis virus 1b (MhV1b) from NRRL 3624; Mucor hiemalis virus 2 (MhV2) from NRRL 3616; and Mucor hiemalis virus 3 (MhV3) and Mucor hiemalis virus (MhV4) from NRRL 3617 strains. Genomes contain two open reading frames (ORF), which encode the coat protein (CP) and the RNA dependent RNA polymerase (RdRp), respectively. In MhV1a and MhV1b, it is predicted to be translated as a fusion protein via -1 ribosomal frameshift, while in MhV4 via a rare +1 (or−2) ribosomal frameshift. In MhV2 and MhV3, the presence of specific UAAUG pentanucleotide motif points to the fact for coupled translation termination and reinitialization. MhV1a, MhV2, and MhV3 are part of the clade representing the genus Victorivirus, while MhV4 is seated in Totivirus genus clade. The detected VLPs in Mucor strains were from 33 to 36 nm in diameter. Hybridization analysis revealed that the dsRNA molecules of MhV1a-MhV4 hybridized to the corresponding molecules.

Sensitivity of Molds From Spoiled Dairy Products Towards Bioprotective Lactic Acid Bacteria Cultures.

Fungal spoilage of dairy products is a major concern due to food waste and economical losses, some fungal metabolites may furthermore have adverse effects on human health. The use of lactic acid bacteria (LAB) is emerging as a potential clean label alternative to chemical preservatives. Here, our aim was to characterize the growth potential at three storage temperatures (5, 16, and 25°C) of a panel of molds (four Mucor and nine Penicillium strains) isolated from dairy products, then investigate the susceptibility of the molds toward 12 LAB cultures. Fungal cell growth and morphology in malt extract broth was monitored using oCelloScope at 25°C for 24 h. Mucor plumbeus 01180036 was the fastest growing and Penicillium roqueforti ISI4 (P. roqueforti ISI4) the slowest of the tested molds. On yogurt-agar plates, all molds grew at 5, 16, and 25°C in a temperature-dependent manner with Mucor strains growing faster than Penicillium strains regardless of temperature. The sensitivity toward 12 LAB cultures was tested using high-throughput overlay method and here all the molds except P. roqueforti ISI4 were strongly inhibited. The antifungal action of these LAB was confirmed when spotting mold spores on agar plates containing live cells of the LAB strains. However, if cells were removed from the fermentates, the inhibitory effects decreased markedly. The antifungal effects of volatiles tested in a plate-on-plate system without direct contact between mold and LAB culture media were modest. Some LAB binary combinations improved the antifungal activity against the growth of several molds beyond that of single cultures in yogurt serum. The role of competitive exclusion due to manganese depletion was examined as a possible antifungal mechanism for six Penicillium and two Mucor strains. It was shown that this mechanism was a major inhibition factor for the molds tested apart from the non-inhibited P. roqueforti ISI4 since addition of manganese with increasing concentrations of up to 0.1 mM resulted in partly or fully restored mold growth in yogurt. These findings help to understand the parameters influencing the mold spoilage of dairy products and the interactions between the contaminating strains, substrate, and bioprotective LAB cultures.

Susceptibility of dairy associated molds towards microbial metabolites with focus on the response to diacetyl

Food spoilage may cause food waste, economic losses and even brand image deterioration. In fermented dairy products, spoilage by molds is frequently occurring and the molds are commonly being introduced at the consumer stage after opening. Diverse molds may be involved with the main genera being Penicillium, Mucor, and Cladosporium. Fungal growth may be inhibited by bioprotective cultures by competition and/or production of inhibitive compounds. Several compounds produced by a range of lactic acid bacteria have been reported as having an antifungal activity against certain fungi. Susceptibility tests of a panel of dairy associated molds towards twelve of these pure compounds were performed using microtiter plate well method. Diacetyl was the most potent antifungal among the compounds followed by octanoic acid. Large variations were seen within the Penicillium strains tested with P. commune being more sensitive than P. roquefortii, and two Mucor strains generally exhibiting high tolerance. The growth of two susceptible Penicillium strains in yoghurt serum with pH 4.6 with increasing amounts of diacetyl added were followed. Susceptibility varied but at 64 μg/mL, both strains were completely inhibited on yoghurt regardless of temperature. At higher pH (5.6) in malt extract agar (MEA), growth was faster but inhibition was still observed. Upon exposure to diacetyl, the level of cytoplasmic reactive oxygen species (ROS) increased and impairment of membrane integrity and leakage of cellular materials were observed. These findings provide new knowledge of the activity of diacetyl against molds.

Industrial applications of selected JFS articles

Industrial applications of selected <i>JFS</i> articles

Sugarcane by-products within the biodiesel production chain: Vinasse and molasses as feedstock for oleaginous fungi and conversion to ethyl esters

Oleaginous microorganisms pose a number of technical advantages when compared to first generation oil crops, but a common drawback to their utilization is often linked to the high operational costs involved in media preparation, using mostly industrial-grade sugars as carbon sources. Considering the abundance of by-products generated by the sugarcane industry, the combined use of molasses and vinasse is suggested in this work as culture medium for the fungal strain Mucor circinelloides URM 4182. Results demonstrate that a 3:1 vol% medium (vinasse to diluted molasses ratio) with minor supplementation of organic nitrogen can provide values within the range of 5 g L−1 of oil-rich biomass with 25 wt% of lipids. The microbial oil was then analyzed in terms of fatty acid profile, demonstrating a favorable composition for biodiesel production, and was subjected to simultaneous esterification and transesterification assays using ethanol and heterogeneous catalyst (H3PMo/Al2O3) in a pressurized reactor, demonstrating satisfactory conversions (>95%). The purified ethyl esters possessed viscosity and density values within the regulating standards and lack of triacylglycerols, suggesting a potential biodiesel production system that could be coupled within sugarcane ethanol facilities.

Comparative aroma and taste profiles of oil furu (soybean curd) fermented with different mucor strains

The effects of different mucor strains (Mucor racemosus, Actinomucor, and Mucor wutungkiao) on aroma and taste profiles based on proteolysis, lipolysis, and their catabolism in oil furu were studied. Gas chromatography-mass spectrometry and relative odor activity were used to monitor the changes of key volatile compounds and the differences in the characteristic aroma contents of oil furu. Using principal component analysis, the different fermentation strains had an effect on aroma profiles. The volatile compounds from metabolism of protein and fatty acid contributed to the aroma of oil furu with different contribution from the different strains, presumably due to their different enzymes. The electronic tongue and free amino acid profiles also showed strain differences of taste. Based on these results, optimization of the amount of each of the different mucor strains during cofermentation might achieve better flavor.

Effects of different strains and fermentation method on nattokinase activity, biogenic amines, and sensory characteristics of natto.

Nattokinase activity(NK), biogenic amine content and sensory properties of natto are of great significance to consumers, which are affected by strains and fermentation methods. In this study, changes in the pH, biogenic amine and free amino nitrogen (FAN) contents, NK and protease activities, and sensory characteristics of natto prepared using Bacillus subtilis GUTU09 combined with different strains (Lactobacillus, Bifidobacterium and Mucor) and fermentation methods were investigated. The combination of two strains showed the best fermentation performance among all samples. The NK and protease activity and FAN content in double-strain fermentation increased by 10.33FU/g, 88.78U/g, and 2.34g/kg, respectively, compared with those in single-strain fermentation. Sensory evaluation demonstrated that mixed fermentation primarily affected the sensory acceptance. This method also reduced the contents of various biogenic amines in natto compared with single-strain fermentation. Tyramine, cadaverine, spermine, and spermidine were significantly reduced, whereas histamine was slightly increased. The total biogenic amines decreased from 390.76mg/kg to a minimum of 16.16mg/kg. Some Mucor strains also reduced the contents of various biogenic amines. In the dual-bacteria fermentation of Mucor and GUTU09, co-fermentation has advantages over stage-fermentation, with higher NK and protease activity and higher sensory scores. Correlation analysis showed that the formation and accumulation of some biogenic amines in natto prepared using different microbial combinations were related to NK activity and pH. All these results showed that the quality of natto was improved by mixed fermentation and suitable fermentation methods, which laid a foundation for its potential industrial application.

Production of Extracellular Rennin-Like Enzyme by a Newly Isolate Mucor circinelloides (von Tieghem) and its Application in Camembert Cheese Making

Introduction: Aspartic proteases produced by different non-pathogenic fungi belonging to mucorales, are commonly used as milk-coagulants. The present study aims to optimize conditions for milk-clotting protease production by a new strain of Mucor genus and to assess its ability in soft cheese making. Materials and Methods: About 20 fungal strains isolated from soil were investigated for their potential to produce milk-clotting proteases for further applications in cheese making. The hyper producer strain Mucor circinelloides 2095-2047 was selected for optimization of rennin-like enzyme production under solid-state fermentation (SSF) using the stepwise modifications of the selected parameters. The enzyme produced under the optimal conditions was partially purified and then applied in Camembert cheese making trials compared to the crude extract and commercial rennet. Results: The maximum milk-curdling activity achieved after optimization (571.43 SU/mL) was obtained using wheat bran (10 g) as the mainly source of carbon containing 1% galactose; moistened with the M-9 solution (pH 6.0) and incubated at 30°C for 96 hours. The enzyme of M. circinelloides was partially purified with a high recovery of 105% and 6.23-fold purity after (NH4)2SO4 fractionation and dialysis. The physicochemical properties of the three produced cheeses were very close. A low sensory quality of cheese was obtained with the crude extract which was getting better using the pre-purified enzyme. This extract was able to develop a very close or even a similar sensory quality to that obtained by the commercial rennet. Conclusions: According to findings, it is possible to propose the purified enzyme of M. circinelloides as a new alternative for rennet, but further optimization, purification and cheese production tests are required.

Dual production of polyunsaturated fatty acids and beta-carotene with Mucor wosnessenskii by the process of solid-state fermentation using agro-industrial waste

Solid-state fermentation is a technique employing microorganisms grown on a solid substrate in the absence of free water. The substrates used in this process are mostly waste from the agro-industry (brans, spent malt grains, distiller grains, etc.) that improves not only the economy of the process but also has positive effect on waste management problems. Zygomycetous fungi are not only able to grow in such conditions but also enrich fermented materials with various types of bioactive compounds. Mucor sp. strains have been identified as producers of gamma-linolenic acid and beta-carotene in submerged fermentation. The aim of the present study was to identify the best microbial producer of gamma-linolenic acid and beta-carotene among four different Mucor strains and to study the requirements for the dual production of these metabolites. Mucor wosnessenskii was identified as the most suitable producer of both metabolites. After optimization of the fermentation conditions, the highest yields obtained were 10.7 g of gamma-linolenic acid/kg of fermented product and 261.5 mg of beta-carotene/kg of fermented product. This yield of beta-carotene is the highest among the results published so far.

A binary copper(II) complex having stepped polymeric structure: Synthesis, characterization, DNA-binding and anti-fungal studies

A rarely found polymeric complex of copper(II) was obtained in the reaction of 2-(4-methylphenyl)acetate and copper sulfate and crystallized in quantitative yield. The complex was characterized using FT-IR, electron spin resonance, absorption spectroscopy, electrochemistry and powder and single crystal XRD studies. The structure was found to consist of interconnected paddlewheel units without an intervening ligand resulting in a stepped polymeric arrangement of the structure. The purity of the sample was judged from powder XRD data while ESR spectroscopy indicated a weak signal between 3000 and 4000 G values, indicating the presence of Cu(II) in the complex. Electrochemistry revealed an irreversible, predominantly diffusion controlled CuIICuII/CuIICuI process with a D0 value calculated to be 3.032?10-8 cm2 s-1. The complex was screened for its DNA-binding ability through cyclic voltammetry, absorption and florescence spectroscopy and viscometry; the former two yielding Kb values of 3.34?103 and 6.90?103 M-1, respectively. The complex exhibited significant activity against fungal strain Mucor piriformis, moderate activity against Aspergillus niger and slight activity against Helminthosporium solani. These preliminary findings revealed the excellent biological potential of the synthesized complex.

PURIFICATION AND BIOCHEMICAL CHARACTERIZATION OF ASPARTIC PEPTIDASE PRODUCED BY NOVEL ISOLATE MUCOR CIRCINELLOIDES (VON TIEGHEM) USING SSF PROCESS

Microbial peptidases are among the most important hydrolytic enzymes which have a potential application in a wide number of industrial processes. In this study, the milk-clotting enzyme of a newly isolated strain Mucor circinelloides (von Tieghem) MG603064 was produced by solid-state fermentation using wheat bran as the substrate. The crude extract exhibited a maximum milk-clotting activity of 1500 ± 50.943 SU/mL after 72 h of incubation at 25 °C. Purification of the enzyme using fractionation at 20‒70% (NH4)2SO4 followed by size exclusion chromatography on Sephadex G-100 allowed us to obtain a 20-fold purified peptidase with a recovery of 18.41%. The highest activity of the purified enzyme (30 kDa) was obtained in 25 mM CaCl2, at pH 5.0 and temperature of 60 °C. The enzyme was stable between pH 3.0‒4.0 for 24 h at 4 °C in 0.1 M citrate buffer and retained more than 80% of its maximum activity at 45 °C for 1 h with complete inactivation at 75 °C. The enzyme inhibition of 94.5 and 98.6% by 0.02 and 0.1 mM Pepstatin A, respectively, confirmed that the enzyme is an aspartyl peptidase. A partial inhibition of 78.17% was noted for EDTA at 14 mM. The enzyme activity was improved significantly by Mg2+, Fe2+, Mn2+ and Zn2+ by 40.5, 59.5, 75.6 and 85%, respectively, and strongly inhibited by Al3+ (93.1%) and Hg2+(94.4%), at a concentration of 10 mM. Activity stimulation of 120% was maximum in the presence of Ba2+ using the same concentration. The crude and pre-purified extracts were applied in a trial of semi-hard cheese making (type Edam) as possible rennet substitutes.

Regulation of quality and biogenic amine production during sufu fermentation by pure Mucor strains

Natural fermentation of sufu yields large amounts of biogenic amines (BAs) and other risk factor, which pose significant health risks. To improve the safety and quality of sufu, we investigated sufu fermentation by three microbial strains, Actinomucor elegans, Mucor wutunkiao, and Mucor racemosus, and monitored the dynamics change of each risk factor during sufu fermentation. Results showed that the moisture content, pH, NaCl, amino acid nitrogen content, and total acid content of all samples were at normal levels for mature sufu products. The H2S and total volatile base nitrogen (TVB-N) levels in Mucor racemosus fermented sufu (MRFS) were lower than those in other mucor fermented sufu. And pure mucor fermentation significantly reduced the benzoic acid content. Different mucor strains and fermentation processes contributed to different BAs levels in the final sufu products. The levels of common BAs cadaverine, spermidine, spermine, histamine, and tyramine were significantly lower (p < 0.05) in MRFS than in sufu fermented with other mucor strains. Through these results, the main step of risk factor generation during sufu fermentation was identified, which can be useful for producing sufu products with good quality and low levels of BAs through pure-culture fermentation.

Leucothrix arctica sp. nov., isolated from Arctic seawater.

A Gram-stain-negative, non-motile, oxidase- and catalase-positive, rod-shaped bacterium was isolated from a coastal seawater sample from the Arctic Circle and designated strain IMCC9719T. On the basis of 16S rRNA gene sequence analysis, it was shown that strain IMCC9719T belonged to the genus Leucothrix and was closely related to the type strains of Leucothrix pacifica (97.6 % similarity) and Leucothrix mucor (95.1 %), while the strain shared <90.6 % sequence similarity with other bacterial species. The average nucleotide identity and genome-to-genome distance values between strain IMCC9719T and L. pacifica JCM 18388T were 71.7 and 16.9 %, respectively. The DNA G+C content of strain IMCC9719T was 43.5 mol%. Optimum growth of strain IMCC9719T was observed at 15 °C, at pH 7.5-8.5 and in the presence of 2.0-2.5 % (w/v) NaCl. The major fatty acids were summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c), summed feature 8 (C18 : 1ω6c and/or C18 : 1ω7c) and C16 : 0. Cells of strain IMCC9719T contained diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, an unidentified polar lipid, an unidentified aminophospholipid and two unidentified phospholipids. The major respiratory quinone was ubiquinone-8 (Q-8). Based on the taxonomic data collected in this study, strain IMCC9719T represents a novel species of the genus Leucothrix, for which the name Leucothrix arctica sp. nov. is proposed. The type strain is IMCC9719T (=KACC 18010T=NBRC 110382T).