| Abstract (English): |
Kitchen garbage is usually discharged from restaurants, public catering rooms and school canteens, and it is reported that 2000 t kitchen garbage would be produced per day in Beijing, China. In other big cities similar phenomena can be observed, and it is reported that half of the municipal waste is composed of kitchen garbage. Kitchen garbage is characterized by high moisture content, easily deteriorating and abundant in nutrition, but it should be treated as a kind of resource rather than simple waste because it is mainly composed of starch, protein, cellulose, fat, and trace element, such as potassium (K), sodium (Na), calcium (Ca), magnesium (Mg), and iron (Fe); kitchen garbage can be regarded as a suitable substrate for microbial growth. In this research, kitchen garbage was used as the raw material to produce Bacillus thuringiensis (Bt) bio-pesticide which is one of the most commonly used and extensively studied bio-pesticides because of its various field applications, such as in agriculture, forestry, and public health sectors. However, the costly raw materials, high equipment investment, and complicated operation procedures in traditional Bt production process have seriously constrained its use at the industrial production scale. In this work we conducted to determine the potential and superiority of using kitchen garbage for Bt bio-pesticide production through semi-solid fermentation to reduce the production cost, and the effects of several parameters on the stability of the product were also studied. In this work, the semi-solid state sample with 75% water content presented the highest δ-endotoxin efficiency of 833 μg/mL, which increased by 54% compared to that of the solid-state sample (water content of 50%) and 162% compared to that of the submerged sample (water content of 99%), and proved that using kitchen garbage as the raw material for Bt production through semi-solid state fermentation has obvious advantages compared with traditional techniques and some similar studies. Mainly because of its nutritious substrate and effective fermentation mode, this technology can not only solve the problem of civil solid waste pollution but also bring a cost-effective resource for Bt bio-pesticide production. Among the main affecting factors during Bt bio-pesticide manufacturing and application, salinity, pH value and temperature had the minimal impact on the stability of the parasporal crystal; when these 3 factors were controlled at 3%, 11 and 60 ℃, respectively, the entomotoxicity of parasporal crystal could still remain above 70% after the fermentation of less for 48 h, and therefore common fermentation process would not inactivate the goal product sharply. By contrast, ultraviolet irradiation had more significant impact on parasporal crystal’s stability, and the entomotoxicity of parasporal crystal declined by 50% when exposed to the ultraviolet (36 W, 60 μW/cm2, 40 cm) for about 3 h. On account of this, polylactic acid was used as the carrier to produce Bt slow-release formulation to mitigate the effects of ultraviolet. Experiments showed that the activity of Bt slow-release formulation remained over 75% of its initial value after 72 h ultraviolet irradiation, which was 10 times the untreated parasporal crystal. And the release rates of parasporal crystal in formulation were generally metastable in a 30-day period, and the compact structure of polylactic acid was proven to effectively protect δ-endotoxin from ultraviolet damage. [ABSTRACT FROM AUTHOR] |