Extracellular Polysaccharide Produced by Lactobacillus Sakei CY1 for Binding Soil Particles

Microorganisms have been used to improve soil structure in sandy soils; extracellular polysaccharide (EPS)-producing bacteria are believed to be useful for improving soil water-holding capacity. Some industries have already produced polysaccharides like xanthan and chitosan from microbes, but for economic reasons, growing microorganisms in situ to directly produce EPS is being considered. In this paper, we examined Lactobacillus sakei, a facultative anaerobic bacterium, as a potential producer of EPS in situ. Lactobacillus sakei strain CY1 is a member of a genus of microaerophilic bacteria known as food fermentation starters, which can produce bacteriocin and secrete polysaccharides. To determine the success of L. sakei CY1 as a biological agent for the improvement of soil quality, we examined the effect of L. sakei CY1 on soil aggregation in indoor experiments. The extent of aggregation was determined after 28 days of cultivation using a variety of carbon sources, such as glucose, fructose, galactose, xylose, and sucrose, on soil media. We compared these results with those obtained using organic fertilizer and commercial soil stabilizers like xanthan and chitosan. When the optimum nutrient sources were used in soil media (sucrose as a carbon source and ammonium chloride as a nitrogen source), the EPS-producing bacteria were just as successful at binding soil particles as the commercial soil stabilizers xanthan and chitosan. Lactoacillus sakei CY1 had caused 75 - 85% of soil particles to adhere to each other and build up macro-aggregates (> 250 μm). These results indicate that in sandy soils, L. sakei CY1 can potentially be used as a binder to improve soil structure.