Ethylene Removal at Low Temperatures under Biofilter and Batch Conditions

Abstract

ABSTRACT Removal of the plant hormone ethylene (C 2 H 4 ) is often required by horticultural storage facilities, which are operated at temperatures below 10°C. The aim of this study was to demonstrate an efficient, biological C 2 H 4 removal under such low-temperature conditions. Peat-soil, acclimated to degradation of C 2 H 4 , was packed in a biofilter (687 cm 3 ) and subjected to an airflow (∼73 ml min −1 ) with 2 ppm (μl liter −1 ) C 2 H 4 . The C 2 H 4 removal efficiencies achieved at 20, 10, and 5°C, respectively, were 99.0, 98.8, and 98.4%. This corresponded to C 2 H 4 levels of 0.022 to 0.032 ppm in the biofilter outlet air. At 2°C, the average C 2 H 4 removal efficiency dropped to 83%. The detailed temperature response of C 2 H 4 removal was tested under batch conditions by incubation of 1-g soil samples in a temperature gradient ranging from 0 to 29°C with increments of 1°C. The C 2 H 4 removal rate was highest at 26°C (0.85 μg of C 2 H 4 g [dry weight] −1 h −1 ), but remained at levels of 0.14 to 0.28 μg of C 2 H 4 g (dry weight) −1 h −1 at 0 to 10°C. At 35 to 40°C, the C 2 H 4 removal rate was negligible (0.02 to 0.06 μg of C 2 H 4 g [dry weight] −1 h −1 ). The Q 10 (i.e., the ratio of rates 10°C apart) for C 2 H 4 removal was 1.9 for the interval 0 to 10°C. In conclusion, the present results demonstrated microbial C 2 H 4 removal, which proceeded at 0 to 2°C and produced a moderately psychrophilic temperature response.