Improvement of vegetable waste composting performance by the addition of hydrolase-producing bacteria

Large quantities of organic waste are produced in modern society and its disposal poses serious environmental and social problems. Malaysia recorded a total volume of 16 metric kilotons per day in food waste. Given this situation, it is crucial to research how food waste degrades, especially vegetable waste, which accounts for nearly half of all food waste produced and poses a serious risk to the environment due to the release of gases and pollutants as well as the potential for infection. This study aimed to isolate hydrolase-producing bacteria (HPB) to improve biodegradation of vegetable waste. A total of 26 bacterial strains were tested through isolation from fermented vegetables, agricultural soils, and those from our glycerol stock collections. Two strains identified as Bacillus licheniformis 2D55 and Bacillus xiamenensis Y7 exhibited activities of multi-hydrolytic enzymes which are amylase, protease, lipase, and cellulase. An in-vitro biodegradation kitchen waste was done through solid-state fermentation (SSF). Co-culture fermentation which consists of rice, vegetable waste and both strains selected demonstrated synergistically improved hydrolytic activities during SSF. The hydrolase activities, microbial count, percentage of biodegraded total solids and gross degradation rate in co-culture treatments were observed superior to the respective mono-cultures and uninoculated control. The co-culture treatments had the highest proportion of biodegraded total solids in sterile SSF (54.73%) and non-sterile SSF (65%) as well as the highest gross degradation rate percentage in sterile SSF (25.39%) and non-sterile SSF (41.36%) after the 14-day fermentation process. The composting process was done in two months and various parameters (moisture content, pH, temperature, microbial count, carbon to nitrogen (C/N) ratio and percentage of biodegraded total solids) were observed and maintained throughout the experiment. In the composting experiment, the inoculated compost was observed superior to the control compost as inoculated recorded higher hydrolase activities and microbial count. In addition, inoculated compost also had higher proportion of biodegraded total solids (63.02%) compared to control (29.80%). Inoculated compost achieved slightly higher temperature during the early stage of composting and with foul odour reduced compared to control. The final inoculated compost was well-matured after two months with germination index, GI (>100%), pH value of around 7, C/N ratio (< 20), dark colour and earthy smell. The overall results demonstrated that inoculating HPB co-cultures not only able to improve vegetable waste biodegradation but also enhancing germination and radical growth.

Text 122809.pdf Download (1MB) Official URL or Download Paper: http://ethesis.upm.edu.my/id/eprint/18672

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