Screening Of Lactobacillus Strains Able To Bind Fumonisins And Possible Mechanisms

Fumonisins (FBs) are a group of water soluble mycotoxins formed mainly by the species fromthe fungus Fusarium. So far,28fumonisins have been identified, in which FB1and FB2, existingwidely in the nature are the most toxic compounds to human body. Fumonisins more often arefound in corn or corn-containing foods. As one of major crops in the world and main sources offood and animal feedings, the fumonisin contamination of corn has caused widespread attention,and is becoming a hot research topic. Various techniques and methods to remove fumonisins areconsidered. However, few reports are developed to use a biological tool to remove fumonisins fromthe surrounding. Therefore, the objectives of this study are to:(1) use ELISA assay and HPLC todetect the adsorption of bacterial cells towards FB1and FB2when48Lactobacillus strains and FB1or FB2are co-cultured at37C for4h;(2) apply2selected strains, i.e., Lactobacillus plantarum ZJ8and Lactobacillus pentosus X5to bind FBs;(3) investigate possible mechanisms of the2lactobacilli strains to bind FBs; and (4) evaluate the effects of fumonisins on the two bacterialgrowth. The following are main results.1. Two Lactobacillus strains showed strong ability to bind fumonisins. The FB1-binding ratewas89.9%for strain ZJ8and86.0%for strain X5. Their FB2-binding rate were95.0%and93.1%,respectively. No interactions between the adsorption of2strains to FB1and FB2were observed,showing that different sites may affect their cells to bind FB1and FB1.2. Physical factors affecting two Lactobacillus strains to bind FB1and FB2included incubationtime, pH and temperature. The maximum FBs-binding percentage of strains ZJ8and X5reached atpH4. Alkaline condition and high temperatures decreased two strains to bind FBs. Meawhile, aconcentration of FB1or FB2ranging from5to10μg/mL in media had no influence on the growthand survival of the two strains. No clear loss in the activity of strains ZJ8and X5was observedafter they were bound to FBs.3. The FBs-binding did not affect the viability of the two strains. Acid and TCA treatmentsleaded to higher FB2-binding percentage than the control did. SDS treatment enabled the twostrains to bind more FB2, but did not enhance their adsorption to FB1. Both lysozyme and trypsintreatments significantly leaded the FB1-Binding percentage of the two strains to decrease. Incontrast, lysozyme treatment improved the two strains to bind FB2. Use trypsin to treat bacterialcells allowed strain X5to bind more FB2. 4. Bacterial cell wall might be responsible for the FBs-binding. It was seen that the cell wall ofstrains ZJ8and X5was able to bind FB1of96.8%and96%, respectively. Their cell walls almostbound whole FB2, i.e.,100%FB2-binding. The FB1/FB2-binding ability of the two lactobacillistrains decreased quickly if their cell walls were removed. Only less than13%FB1and19%FB2were bound to the cell wall-free bacteria. The cell-free extracts of the two lactobacilli strains wereobserved to have a very low FB1/FB2-binding (less than5%). Moreover, peptidoglycan liberatedfrom the cell wall was recognized as the main binding receptor for FBs, and its integrity was veryimportant in binding. The binding percentage of peptidoglycans of the two strains to FB1was98.4%and97.8%, respectively. Almost100%FB2was bound to the peptidoglycans of the twostrains.In conclusions, the selected two Lactobacillus strains showed strong ability to bind fumonisins,and should be very potential as a biological agent for the detoxification of mycotoxins.