Jin Ho Joo

Khalid Abdallah Hussein , Young Don Lee and Jin Ho Joo . J. Microbiol. Biotechnol. 2020;30:. https://doi.org/10.4014/jmb.2002.02013

BACKGROUND: From year 2005, landfill for food waste has been prohibited. Also, according to London agreement in year 2013, ocean discharge for livestock manure, sewage sludge, and food waste has been regulated. Alternative way for food waste disposal is incineration. However, due to high moisture content, additional input for energy is needed. Therefore, effective way for food waste disposal such as application of food waste compost is needed. METHODS AND RESULTS: Seven different treatments (livestock compost, food waste compost, food waste + livestock compost, livestock compost + chemical fertilizer, food waste compost + chemical fertilizer, food waste + livestock compost + chemical fertilizer and control) were applied to tomato crop. All treatments were replicated with completely randomized design. Tomato growth treated with LC+NPK showed the highest values at 6 weeks for all parameters such as leaf length (11.80 cm), leaf width (6.88 cm), and chlorophyll (61.12 O.D.), compared to other treatments. Subsequently the FWC+LC+NPK treatment was followed (11.51 cm, 6.40 cm, 59.50 O.D. for leaf length, leaf width, and chlorophyll, respectably). EC, OM contents, and CEC in the soil treated with the composts significantly increased. CONCLUSION: To evaluate the effect of food waste compost application on tomato growth and soil chemical properties, we carried out field experiment treated with 7 treatments with 3 replicates. The LC+NPK treatment showed highest values for all parameters. Some parameters such as shoot length and total length for tomato were not significantly different between the LC+NPK and the FWC+LC+NPK treatments.

Recently, heavy metals have been shown to have a stimulating effect on siderophore biosynthesis in various bacteria. In addition, several studies have found that siderophore production is greater in bacteria isolated from soil near plant roots. The aim of this study was to compare the production of siderophores by bacterial strains isolated from heavy metal-contaminated and uncontaminated soils. Chrome azurol sulphonate was used to detect siderophore secretion by several bacterial strains isolated from heavy metal-contaminated and rhizosphere-uncontaminated soils with both a qualitative disc diffusion method and a quantitative ultraviolet spectrophotometric method. Siderophore production by rhizosphere bacteria was significantly greater than by bacteria isolated from contaminated soil. The Pearson’s correlation test indicated a positive correlation between the amount of siderophore produced by bacteria isolated from the rhizosphere using the quantitative and qualitative detection methods and the amount of heavy metal in the soil. However, a significant negative correlation was observed between the amount of siderophore produced by bacteria isolated from heavy metal-contaminated soil and the amount of heavy metal (r value of −0.775, P < 0.001).

Microorganisms exposed to heavy metal stress are vulnerable to the toxic conditions caused by reactive oxygen species. The aim of this study was to investigate the tolerance of stressed bacteria and detect the ability of some resistant bacterial strains to produce antioxidant enzymes under heavy metal stress. The minimum inhibitory concentration (MIC) of heavy metals and antibiotic sensitivity were investigated for some bacterial strains isolated from a heavy metal-polluted area. Moreover, the activities of antioxidant enzymes produced in the resistant bacterial strains were measured. The most toxic heavy metals found using the MIC test were Cd2+ followed by Co2+. The MIC of all heavy metals except Pb2+ and Zn2+against the most metal-resistant bacteria species ranged from 300 to 500 mg/L. In addition, 100 mg/L Zn2+ or Pb2+ increased and induced the activity of the antioxidant enzymes catalase, peroxidase and ascorbate peroxidase. The strain Pseudomonas putida KNU5 greatly induced ascorbate peroxidase (1,030%) under the stress of 100 mg/L Zn2+, while the activity of ascorbate peroxidase decreased to 115% under 100 mg/L Pb2+. Thus, heavy metals cause oxidative stress in P. putida and antioxidant enzymes appear to play a pivotal role in combating oxidative stress, providing protection to P. putida. Furthermore, the results of this study show that antioxidant enzymes can be used to biologically monitor heavy metal pollution. Key words: Heavy metals, resistant bacteria, antioxidant enzymes.