Production of Levan by Bacillus licheniformis for Use as a Soil Sealant in Earthen Manure Storage Structures

Abstract

Manure application is not permitted on frozen land in Canada and therefore, manure management and storage are the primary issues facing the agri-food industry. Low-cost, effective and environmentally safe earthen manure storage (EMS) facilities will lower costs and help make the livestock industry more competitive and efficient. The goal of this study was to develop a biological sealing technology for earthen manure storages. The results showed that it is feasible to use a growing culture of Bacillus licheniformis to produce a non viscous water insoluble levan. Levan can only be produced by Bacillus licheniformis during the growth mode. No levan was produced during the death phase. About 0.36 g of levan was produced per gram of sucrose which is 91.1% of theoretical yield. The polymer can be used as a plugging agent to plug the pores of high permeability soils. From the biological and biochemical characteristics of the Bacillus licheniformis, it appears that the organism is capable of producing levan from sucrose under most field and soil conditions. As a soil organism, Bacillus licheniformis should be able to compete with most common soil species such as Arthrobacter and Bacillus. The bacteria could be grown either in the non-polysaccharide producing mode or in the polysaccharide producing mode. The first would permit distribution of the bacteria to the lower soil layers but would delay the production of the polysaccharide due to the lag period required to produce the enzyme (levansucrase). Upon production of levan, pore spaces would close and hence, the hydraulic conductivity would be substantially reduced.