Screening of Lactic Acid Bacteria for Anti-Fusarium Activity and Optimization of Incubation Conditions

Anti-Fusarium activities of lactic acid bacteria (LAB) Lactobacillus plantarum 299V, L. plantarum NRRL-4496, and Lactobacillus rhamnosus VT1 were determined by a microdilution assay developed in this study against Fusarium graminearum 08/RG/BF/51. A cell-free Lactobacillus culture supernatant (CFLCS) of L. rhamnosus VT1 had the highest anti-Fusarium activity. Response surface methodology was used to optimize the incubation conditions for production of CFLCS. A Box-Behnken factorial design was used to investigate the effects of incubation time, shaking speed, and incubation temperature on the inhibition rate of CFLCS. A model equation was generated to predict the inhibition rate of CFLCS under various incubation conditions. A low probability value (0.0012) and associated F value of 25.10 suggested that the model was highly significant. A high R-2 value (0.978) indicated a very satisfactory model performance. Response surface methodology analysis suggested that an incubation temperature at 34 degrees C, a shaking speed at 170 rpm, and an incubation time of 55 h were the best combination for production of CFLCS from L. rhamnosus VT1. Under these incubation conditions, a 10% L. rhamnosus VT1 CFLCS solution was predicted to inhibit the growth of F. graminearum by 75.6% in vitro and inhibited 83.7% of the growth in the validation experiment. Thus, the CFLCS of L. rhamnosus VT1 was an effective anti-Fusarium mixture.