One-way analysis of variation (ANOVA) was conducted using SAS software 9.2 to compare the level of glycerol, succinic acid and acetic acid between different mutants with the level of metabolites in the wild-type strain with mean values compared using the Dunnett test (p b 0.05). Tukey test (p b 0.05) was performed to compare the significant difference between the level of metabolites for all mutants and the wild-type strain. For Rheofermentometer parameters, verification of significant differences was done by Tukey test at a 5% significance level.