Glass bead system to study mycotoxin production of Aspergillus spp. on corn and rice starches.

Mycotoxin production by aflatoxin B1 (AFB1) -producing Aspergillus flavus Zt41 and sterigmatocystin (ST) -hyperproducer Aspergillus creber 2663 mold strains on corn and rice starch, both of high purity and nearly identical amylose-amylopectin composition, as the only source of carbon, was studied. Scanning electron microscopy revealed average starch particle sizes of 4.54 ± 0.635 µm and 10.9 ± 2.78 µm, corresponding to surface area to volume ratios of 127 1/µm for rice starch and 0.49 1/µm for corn starch. Thus, a 2.5-fold difference in particle size correlated to a larger, 259-fold difference in surface area. To allow starch, a water-absorbing powder, to be used as a sole food source for Aspergillus strains, a special glass bead system was applied. AFB1 production of A. flavus Zt41 was determined to be 437.6 ± 128.4 ng/g and 90.0 ± 44.8 ng/g on rice and corn starch, respectively, while corresponding ST production levels by A. creber 2663 were 72.8 ± 10.0 µg/g and 26.8 ± 11.6 µg/g, indicating 3-fivefold higher mycotoxin levels on rice starch than on corn starch as sole carbon and energy sources. KEY POINTS: • A glass bead system ensuring the flow of air when studying powders was developed. • AFB1 and ST production of A. flavus and A. creber on rice and corn starches were studied. • 3-fivefold higher mycotoxin levels on rice starch than on corn starch were detected.

Flavobacterium hungaricum sp. nov. a novel soil inhabitant, cellulolytic bacterium isolated from plough field.

A Gram-negative bacterial strain, named Kb82, was isolated from agricultural soil and a polyphasic approach was used for characterisation and to determine its taxonomic position. Based on 16S rRNA gene sequence analysis, the highest similarity was found with Flavobacterium artemisiae SYP-B1015 (98.2%). The highest ANI (83.3%) and dDDH (26.5%) values were found with Flavobacterium ginsenosidimutans THG 01 and Flavobacterium fluviale HYN0086T, respectively. The isolate is aerobic with rod-shaped cells, positive for catalase and negative for oxidase tests. The DNA G+C content is 34.7 mol%. The only isoprenoid quinone is menaquinone 6 (MK-6). The major fatty acids are iso-C15:0, summed feature 3 (C16:1 ω7c/C16:1 ω6c) and iso-C17:0 3OH. The major polar lipid is phosphatidylethanolamine. On the bases of phenotypic characteristics and analysis of 16S rRNA gene sequences, it is concluded that strain Kb82T represents a novel species in the Flavobacterium genus, for which the name Flavobacterium hungaricum sp. nov. is proposed. The type strain of the species is strain Kb82T (= LMG 31576T = NCAIM B.02635T).

Sphingobacterium hungaricum sp. nov. a novel species on the borderline of the genus Sphingobacterium.

A Gram-reaction-negative bacterial strain, designated Kb22T, was isolated from agricultural soil and characterized using a polyphasic approach to determine its taxonomic position. On the basis of 16S rRNA gene sequence analysis, the strain shows highest similarity (94.39 %) to Sphingobacterium nematocida M-SX103T. The highest average nucleotide identity value (71.83 %) was found with Sphingobacterium composti T5-12T, and the highest amino acid identity value (66.65 %) was found with Sphingobacterium olei HAL-9T. Cells are aerobic, non-motile rods. The isolate was found to be positive for catalase and oxidase tests. The assembled genome of strain Kb22T has a total length of 4,06 Mb, the DNA G+C content is 38.1 mol%. The only isoprenoid quinone is menaquinone 7 (MK-7). The major fatty acids are iso-C15:0 (28.4%), summed feature 3 (C16:1 ω7c and/or iso-C15:0 2-OH) (25.7 %) and iso-C17:0 3-OH (19.7 %). Based on phenotypic characteristics and phylogenetic results, it is concluded that strain Kb22T is a member of the genus Sphingobacterium and represents a novel species for which the name Sphingobacterium hungaricum sp. nov. is proposed. The type strain of the species is strain Kb22T (=LMG 31574T=NCAIM B.02638T).

Sphingobacterium pedocola sp. nov. a novel halotolerant bacterium isolated from agricultural soil.

A Gram-reaction-negative halotolerant bacterial strain, designated Ka21T, was isolated from agricultural soil and characterised using a polyphasic approach to determine its taxonomic position. On the basis of 16S rRNA gene sequence analysis, highest similarity was found with Sphingobacterium alkalisoli Y3L14T (96.72%). Cells were observed to be aerobic, non-motile rods. The isolate was found to be able to grow between 0 and 10% of NaCl concentration. The assembled genome of strain Ka21T has a total length of 5.2 Mb with a G + C content of 41.0 mol%. According to the genome analysis, Ka21T encodes several glycoside hydrolases that may play a role in the degradation of accumulated plant biomass in the soil. Based on phenotypic characteristics and phylogenetic analysis, it is concluded that strain Ka21T represents a novel species in the Sphingobacterium genus for which the name Sphingobacterium pedocola sp. nov. is proposed. The type strain of the species is strain Ka21T (= LMG 31575T = NCAIM B.02636T).

Aflatoxin B1 and Sterigmatocystin Binding Potential of Non-Lactobacillus LAB Strains.

Research on the ability of lactic acid bacteria (LAB) to bind aflatoxin B1 (AFB1) has mostly been focusing on lactobacilli and bifidobacteria. In this study, the AFB1 binding capacities of 20 Enterococcus strains belonging to E. casseliflavus, E. faecalis, E. faecium, E. hirae, E. lactis, and E. mundtii, 24 Pediococcus strains belonging to species P. acidilactici, P. lolii, P. pentosaceus, and P. stilesii, one strain of Lactococcus formosensis and L.garviae, and 3 strains of Weissella soli were investigated in MRS broth at 37 °C at 0.2 µg/mL mycotoxin concentration. According to our results, among non-lactobacilli LAB, the genera with the best AFB1 binding abilities were genus Pediococcus, with a maximum binding percentage of 7.6% by P. acidilactici OR83, followed by genus Lactococcus. For AFB1 bio-detoxification purposes, beside lactobacilli, pediococci can also be chosen, but it is important to select a strain with better binding properties than the average value of its genus. Five Pediococcus strains have been selected to compare their sterigmatocystin (ST) binding abilities to AFB1 binding, and a 2-3-fold difference was obtained similar to previous findings for lactobacilli. The best strain was P. acidilactici OR83 with 18% ST binding capacity. This is the first report on ST binding capabilities of non-Lactobacillus LAB strains.

Aflatoxin B1 and Sterigmatocystin Binding Potential of Lactobacilli.

Due to global climate change, mould strains causing problems with their mycotoxin production in the tropical-subtropical climate zone have also appeared in countries belonging to the temperate zone. Biodetoxification of crops and raw materials for food and feed industries including the aflatoxin B1 (AFB1) binding abilities of lactobacilli is of growing interest. Despite the massive quantities of papers dealing with AFB1-binding of lactobacilli, there are no data for microbial binding of the structurally similar mycotoxin sterigmatocystin (ST). In addition, previous works focused on the detection of AFB1 in extracts, while in this case, analytical determination was necessary for the microbial biomass as well. To test binding capacities, a rapid instrumental analytical method using high-performance liquid chromatography was developed and applied for measurement of AFB1 and ST in the biomass of the cultured bacteria and its supernatant, containing the mycotoxin fraction bound by the bacteria and the fraction that remained unbound, respectively. For our AFB1 and ST adsorption studies, 80 strains of the genus Lactobacillus were selected. Broths containing 0.2 µg/mL AFB1and ST were inoculated with the Lactobacillus test strains. Before screening the strains for binding capacities, optimisation of the experiment parameters was carried out. Mycotoxin binding was detectable from a germ count of 107 cells/mL. By studying the incubation time of the cells with the mycotoxins needed for mycotoxin-binding, co-incubation for 10 min was found sufficient. The presence of mycotoxins did not affect the growth of bacterial strains. Three strains of L. plantarum had the best AFB1 adsorption capacities, binding nearly 10% of the mycotoxin present, and in the case of ST, the degree of binding was over 20%.

Micrococcoides hystricis gen. nov., sp. nov., a novel member of the family Micrococcaceae, phylum Actinobacteria.

A Gram-stain-positive bacterium, designated TSL3T, was isolated from faeces of a porcupine, Hystrix indica, from the Budapest Zoo and Botanical Garden, Hungary. On the basis of 16S rRNA gene sequence analysis, the strain is phylogenetically related to the family Micrococcaceae. The highest 16S rRNA gene sequence similarity was found with Micrococcus terreus V3M1T (96.50 %) followed by Arthrobacter humicola KV-653T (96.43 %). Cells of strain TSL3T were aerobic, non-motile and coccoid-shaped. The main fatty acids were anteiso-C15 : 0 (54.4 %), iso-C16 : 0 (18.2 %) and iso C15 : 0 (9.7 %). The major menaquinone was MK-7, and the polar lipid profile included phosphatidylglycerol, diphosphatidylglycerol, dimannosylglyceride, trimannosyldiacylglycerol, phosphatidylinositol, three unknown phospholipids and two unknown glycolipids. Strain TSL3T showed the peptidoglycan structure A4alpha l-Lys - Gly - l-Glu. The DNA G+C content of strain TSL3T was 58.4 mol%. Phenotypic and genotypic characterisation clearly showed that strain TSL3T could be differerentiated from the members of other genera in the family Micrococcaceae. According to these results, strain TSL3T represents a novel genus and species, for which the name Micrococcoides hystricis gen. nov., sp. nov. is proposed. The type strain is TSL3T (=DSM 29785T=NCAIM B. 02604T).