Effect of the Extracts from Thai Rice Straw on Growth Inhibition of Toxic Cylindrospermopsis raciborskii NUPLKC32

Abstract

This study was aimed to investigate the growth performance of toxic Cylindrospermopsis raciborskii NUPLKC32 cultivated by medium mixing the rice straw extracts. Factorial experiment was designed with the rice straw extracts from three rice strains (Suphan Buri; KJHSB, RD1 and Phatum Thani; KJHPT) and six different concentrations (0 control, 1, 5, 10, 20 and 30 g/L). The results showed that the cell numbers of C. raciborskii NUPLKC32 were reduced from 99.4 to 100.0% at the KJHSB and RD 1 straw extracts of 10 to 30 g/L, within 14 days, while cell number was reduced only 98.8 (p<0.05) % at the KJHPT straw extract of 30 g/L (p<0.05). When compared with the control, the trichomes of cells cultivated by rice straw extract of each strain were mostly broken and short.  The results of two-way ANOVA exhibited that the interaction between rice strains and concentrations of rice straw extracts affected significantly on the growth of C. raciborskii NUPLKC32 (p<0.05). The tannin contents were highest at the concentration of 30 g/L rice straw extracts. The maximal tannin content (1.39±0.05 mg/L) was found in the KJHSB straw extract.  Considering the results of this present, the rice straw extracts of KJHSB and RD1 strains at the concentration of 10-30 g/L could efficiently inhibit the growth of toxic C. raciborskii NUPLKC32 and these extracts should be developed to natural products in the future.