Biological treatment of waste polychlorinated biphenyls (PCBs) mixed with organic solvents (OSs) requires bacteria that have both OS tolerance and PCB-degrading capacity. Therefore, we tried to find such bacteria strongly capable of both tolerating OS and degrading PCBs. We screened eleven bacteria capable of degrading more than 70% (w/v) of KC-300 containing 10ppm PCB from 200 samples of soil and sea water taken from the mouth of Sagami river and elsewhere. We selected six of the 11 strains that could degrade more than 50% (w/v) of KC-500 (10 ppm). The six strains were subjected to experiments using high concentrations of PCBs (HC-PCBs) and OS tolerance tests. Of these six, a strain that could degrade HC-PCBs was selected, and identified by physiological, biological and electron microscopic examinations as Pseudomonas putida. The isolate was then named SN-4992. SN-4992 degraded more than 60% of PCBs at 100 ppm (KC-400) over 15 d, and 86.8 % of very toxic coplanar PCBs (c-PCBs) in KC-400 (100 ppm).
The survival of Escherichia coil K-12 and Pseudomonas putida BH inoculated into fresh water, sea water, activated sludge, and soil microcosms was studied. Three kinds of microcosms, named as intact, protozoa-free (filtered with 1.0μm filter or 2.0 g/l of cycloheximide added), and sterilized microcosms (filtered with 0.22μm filter or autoclaved twice at 120°C for 20 min.), were made from each kind of environmental sample, and used for the survival studies in order to separately evaluate the general effects of protozoan predation, interaction with indigenous bacteria, and starvation. In the all intact microcosms, both exogenous bacterial populations decreased rapidly by 1 to 4 orders of magnitude over 7 d. The experimental results indicated that the interaction with indigenous bacteria, especially in the form of antagonism or amensalism, was the most influential factor causing the decline of the exogenous bacterial populations, and that the protozoan predation was much less influential. To demonstrate evidence for the presence of such antagonism, heterotrophic bacteria indigenous to each intact microcosms were isolated, and their antagonistic activities against the introduced exogenous bacteria were examined. Approximately 1.0-3.5% of the isolated bacterial strains showed antagonistic activity against either E. coil K-12 or P. putida BH. However, the antagonistic activity exerted by most strains was found to be unstable.
In order to devise a useful method to detect the putrefactive lactic acid bacteria (LAB hereafter) Leuconostoc sp., ten amino acids of high solubility were tested for their effects to inhibit the growth of Leuconostoc mesenteroides. Against L. mesenteroides subsp. mesenteroides IFO3426 (hereafter referred to as MES) the most effective amino acid was histidine, followed by glycine, serine and valine in that order. Histidine, glycine and serine were similarly most effective against L. mesenteroides subsp. dexranicum IFO 3349 (hereafter referred to as DEX). Histidine was regarded as one of the most effective amino acids to inhibit the growth of both strains. It inhibited MES at a concentration of 7% (w/v) and DEX at 5% (w/v). It was inhibitory between 15 and 30°C and between pH7-9, and most inhibitory at pH9. Of the 32 strains of Leuconostoc species other than Leuconostoc oenos examined in this study, 31 strains were inhibited with histidine with the exception being Leuconostoc mesenteroides subsp. dextranicum AHU 1680. Histidines did not inhibit the growth of putrefactive LAB other than L. mesenteroides and Leuconostoc lactis.
Microbial calorimetry was applied to urethane foam-supported cultures of Klebsiella pneumoniae and Aspergillus oryzae to quantitatively evaluate the growth activity of microbes. The amplitude of calorimetric signals observed for the growth of microbes in a medium with porous urethane foam support was found to be markedly greater than that in stationary cultures in ordinary liquid media. For quantitative comparison, the maximal amplitude of the calorimetric signal, the growth rate constant and the doubling time were evaluated from the growth thermograms observed. The result obtained was that the growth activity of K. pneumoniae cultured on urethane foam increased about 10-fold that of cultures in liquid medium, as judged by the thermopile output signal at the peak time and about 1.7-fold in terms of the growth rate constant. The values observed for the supported culture of A. oryzae were about 1.5-fold and about 3-fold higher, respectively. The method was also applied to study the effect of sodium benzoate on the urethane foam-supported culture of A. oryzae, and its inhibitory action was quantitatively discussed.
The heat resistance of Bacillus subtilis 168 spores suspended in several kinds of oil was in-vestigated. In soybean oil, the D value of the thermal death of spores at 98.4°C was 53 min, be-ing about 7 times greater than that in potassium phosphate buffer. The Z value was 71°C in soybean oil but 11°C in the buffer. A similar increase in the D value was observed in other edible oils and n-hexadecane. The differences in the heat resistance of spores among these oils seemed to depend upon the water content of oils even at considerably low levels. Furthermore, the dehydration of oils by dry heat increased the heat resistance of spores. In addition, freeze-dried spores were more resistant to heat than frozen spores in soybean oil. In an open heating system, the spore resistance was higher than that in a closed system. These results suggest that the water content of oil substantially determines the heat resistance of spores suspended in it.
Combined bactericidal effects of acetic acid, temperature, and sodium chloride on Salmonella typhimurium, Staphylococcus aureus and Vibrio parahaemolyticus were examined in processed vinegar. To express their effects, we established quadratic polynomial models distinguished into two types according to the presence or absence of sodium chloride. These models were also evaluated by the alternative variables of acetic acid concentration and pH value. Every model had high values for the correlation coefficients (r2=0.963-0.990) between predicted and observed inactivation rates. The fitness for the model prediction was observed independent of bacterial species, i.e., gram negative, positive, and halophilic bacteria.
Thermal inactivation curves of Aspergillus niger spores and mycelia in phosphate-citrate buffer were studied. Spores were most thermoresistant when suspended at pH 5.0 out of a range of pH 4.0-9.0. At higher salt (sodium chloride) concentrations of 0-0.7 M spores were more resistant. These curves were well described by a thermotolerant subpopulation model and characterized with the parameter values of the model. Catalase and pyruvic acid supplemented in enumeration media or heating menstruum did not raise the survival ratios of heated spores. The thermal inactivation curve of mycelia did not have a shoulder but a tail.
Examination was made of the effects of nine commercial disinfectants in short term application at concentrations recommended for practical use against 34 fungi. The effects of a yeast extract comprised of various organic substances on the efficacy of the disinfectants were also studied. Ethanol (EtOH, 70%, v/v) was found the most effective disinfectant and not influenced by yeast extract at a concentration of 5% (w/v). Oxidizing potential liquid (OPL) with 55μg/ ml as the active chlorine concentration, iodine (IA) at 45μg/ml and sodium hypochloride (NaOCI) at 200μg/ml all showed strong fungicidal effects, which were, however, significantly diminished by yeast extract. Didecyldimethylammonium chloride (DDAC) at 100μg/ml, benzalkonium chloride compounds (BACC) at 285μg/ml and benzalkonium chloride (PBKC) at 200μg/ml had a smaller fungicidal effects but there effects were less altered by the extract. [Mono-bis (trimethylammonium methylene chloride)] -alkyl (C9-15) toluene (MBAT) at 100μg/ml and chlorhexidine digluconate (CHD) at 200μg/ml, showed the smallest fungicidal effects.
The biological resistance of wood plastic composites using methyl-methacrylate and phenolic-resin was evaluated with an emphasis on the structural characteristics of the cell wall after exposure to fungal attack. Differences in the polymer deposition in the wood cellular structure due to combination with plastic exhibited the specific patterns of cell wall erosion caused by decay fungi. Scanning electron microscopic observations confirmed that the smallmolecular weight phenol-formaldehyde (PF) resin easily penetrated the wood and led to the deposit of polymers within the cell walls, resulting in a high resistance to decay. In contrast, the limited levels of penetration of the large-molecular weight PF-resin and the methacrylate resin led to formation of polymer bodies in the cell lumens or the partial surface coatings which contributed little to the decay resistance.
Two chemicals, sodium chloride and hydrogen peroxide were investigated for their efficacies as fungal control agents and compared with malachite green, fungal a control agent commonly used in hatcheries. No significant differences in results were seen between treatment with 1000μg/ml hydrogen peroxide and that with 2μg/ml malachite green in terms of the number of eggs infected and the hatching rate. When compared with the other two chemicals, sodium chloride at 25 ppt showed less effectiveness for fungal control.