The production of Cephalosporin C was investigated in a lab-scale 1.4 / air-lift reactor (ALR), using various immobilization modes. Bioparticles were developed by forming biofilm of growing hyphae around an inorganic siran particle which contained spores of the organism. Silk sachet was the other immobilization matrix. The maximum specific growth rate of the Cephalosporium acremonium, free cells, pellets, siran carrier and silk sachets were 0.037, 0.003, 0.047, and 0.035 h−1, and specific antibiotic productivities (as compared to 100% for free cells) were 180, 150, and 125% for siran carrier, silk sachets and pellets, respectively. Immobilization modes exhibited enhanced volumetric oxygen transfer coefficient and well-controlled, three-phase hydrodynamics.
A nucleic acid-based method was evaluated in the course of a study of microbial community structure in the cricket hindgut. Genomic DNA was extracted from the hindgut microbial community of Acheta domesticus and used as a template in the polymerase chain reaction (PCR) method, using primers that align to well conserved regions of the 16S rRNA gene. The rDNA-PCR product was used as a community probe to generate restriction fragment length polymorphisms (RFLPs) of hindgut bacterial isolates and gut microbial communities of insects fed different diets. Fingerprints of the bacterial isolates consisted of several bands suggesting multiple rRNA operons. In contrast with soil communities, hindgut community RFLP contained distinguishable band patterns. However, community rDNA fingerprints were complex and varied among insects fed similar diets, suggesting considerable intrinsic variability in the hindgut microbial community structure between crickets regardless of dietary regime. These results suggest that community RFLP methods using broad-specific phylogenetic probes do not have the resolution or specificity required to ascertain the effect of diet on the cricket hindgut microbial community structure.
Fifty-three strains of actinomycetes resistant to heavy metals were isolated from the Salí River in northwest Argentina. Screening procedures that involve solid and liquid synthetic media containing Cd2+, Cu2+, or Hg2+ allowed the selection of six strains. These strains showed a quantitative sorption of Cd2+ and Cu2+ by more than 98% of the initial metal concentrations (0.1, 0.5, and 1.0 mM) tested.
To isolate naturally occurring novel Bacillus thuringiensis strains, we investigated the distribution and characteristics of B. thuringiensis from samples of sericultural farms in various regions of Korea in the spring and fall. Fifty-four B. thuringiensis strains out of 164 samples and 34 B. thuringiensis strains out of 135 samples were isolated in the spring and fall, respectively. Seventy percent of the isolates in the spring and 15% in the fall were toxic to lepidopteran larvae. Dipteran-active isolates were rare (7% in spring and 3% in fall isolation). Particularly, B. thuringiensis isolates, which are toxic to both Lepidoptera and Diptera, were widely distributed (19% in spring and 62% in fall isolation). Non-toxic isolates were also found (4% in spring and 20% in fall isolation). B. thuringiensis isolates in the sericultural farms represented 11 H serotypes; they were principally B. thuringiensis subsp. aizawai in the spring and kurstaki in the fall. B. thuringiensis isolates of serotypes 1, 3a, 3a3b, 4a4c, 6, 7 and 12 were toxic to Lepidoptera. Seventy isolates produced typical rhomboidal inclusions, and the remainder produced parasporal inclusions with various morphologies. PCR analysis using cryI gene type-specific primers showed that cryIAa and cryIC genes are frequently found in the spring and cryIAa gene is a predominant type in the fall. Toxicity, H serotype and the cryI gene contents of B. thuringiensis isolated from sericultural farms showed that distribution varied depending on the season.
The production of lipase from Acinetobacter calcoaceticus LP009, a bacterium isolated from raw milk, was found to be best induced by Tween-80 at 1.0% concentration. It was efficiently secreted, and only a minute amount of activity was detected at the cell surface and intracellularly. A. calcoaceticus LP009 lipase exhibited maximum activity at pH 7.0 and 50°C, and was relatively stable upon storage at pH 5.0 to 7.0 and at 4, 30, or 37°C. The enzyme was found to be inactivated by EDTA suggesting that it was a metalloenzyme. Its activity was reduced by less than 20% with the addition of various ions to reaction mixtures, but long storage with them caused approximately 50% reduction in subsequent reactions under standard conditions. By contrast, the addition of Fe3+ enhanced activity. The enzyme was highly stable upon storage with 0.1% of Triton X-100, Tween-80 or Tween-20, but highly unstable with various organic solvents tested. PMSF, a serine enzyme inhibitor, and 2-mercaptoethanol, a reducing agent, did not affect enzyme activity. After extraction and transfer, the lipase gene was efficiently expressed in recombinant Aeromonas sobria. This recombinant strain was shown to have increased hydrolyzing efficiency and have high potential for lipid-rich wastewater treatment.
Fatty acid esters composed of sterically hindered alcohol are very poor substrates for known lipases. In order to obtain a novel lipase, t-butyl octanoate (TBO) was selected as a model substrate to screen for bacteria-producing lipase(s) which can preferentially hydrolyze bulky esters. Of 279 strains isolated from 350 soil samples based on the ability to grow with TBO as a sole carbon source, one strain (YY62) was chosen for its strong TBO-hydrolyzing activity. Strain YY62 is a Gram-negative motile rod and was identified as Burkholderia sp. from the taxonomic characters and phylogenetic analysis of 16S rDNA nucleotide sequences. Using the activity ratio between TBO and p-nitrophenyl acetate as a measure for preference to bulky esters, we confirmed that the lipase of strain YY62 was 100-fold superior to commercial lipases in terms of TBO-hydrolyzing activity.
Thirty-six isolates of Leuconostoc spp. were isolated from yellow spots that occurred on the surface of vacuum-packaged ham. All isolates were Gram-positive, catalase-negative cocci that produced gas from glucose and formed more than 90% of their lactate as D(−) isomer. These isolates could grow at 4°C but not above 30°C and most strains produced yellow spots on the ham. The isolates were divided into three groups by sugar fermentation patterns. Representative strains from three groups showed intergroup DNA homology values of above 88.8%, showing that these groups were composed of a single species. This organism was positioned at a separate branch in the genus Leuconostoc on the phylogenetic tree based on 16S rRNA sequences, which was assigned to Leuconostoc gelidum on the basis of DNA-DNA relatedness.