Fig. 4 shows the effect of rhamnolipid production factor levels on the grey grade. Basically, the larger the

grey relational grade, the better the multiple performance characteristics. A higher grey relational grade indicates that the corresponding S/N ratio is closer to the normalized S/N ratio which in return corresponds to a characteristic setup closer to optimal [22]. Step 7: Finally, by considering the maximization of grade values (by using Eq. (10)) as per shown in Table 7 and Fig. 4, we could obtain the optimal process parameter conditions as A2B2C1 i.e., a TS of 20% (w/v), C/N ratio of 20 and incubation time of 3 days. Table 9 compares the experimental results of the optimal parameter combinations derived using Taguchi method and grey relational Dasatinib ic50 analysis. As shown in the table, the improvement of 3% was exhibited in rhamnolipid yield, increasing from 1.45 (Taguchi method) to Selleckchem BGB324 1.50 g/L (grey relational analysis); and 142% in volumetric productivity.

Also, the biomass formation was suppressed up to 33%. It is worth noting that in simple Taguchi method, the maximum rhamnolipid yield (1.45 g/L) was observed at 7 days of incubation, whereas when integrated with GRA an enhanced rhamnolipid amount (1.50 g/L) was obtained just at 3 days of incubation. This reduced the process duration by 57.14%, which resulted in improved process productivity. The ANOVA is successfully applied to investigate which rhamnolipid production parameter significantly affects the performance

characteristic. The ANOVA analysis in Table 8 and percentage contributions for each term affecting grey relational grade (Fig. 5) indicate that the TS concentration and incubation time are the significant rhamnolipid production process parameters affecting the multiple performance characteristics. Furthermore, the TS concentration is the most significant process parameter due to its highest percentage contribution (of 50%) among the process parameters. Based on the above discussion, the optimal rhamnolipid production process parameters were total sugars concentration (2% w/v) at level 2, C/N ratio (20) at level 2 and incubation Sinomenine time (3 days) at level 1. After the optimal level of the different factors is selected, the final step was to predict the performance characteristic using the optimal level of factors. As none of the experiments shown in Table 2 fits the optimal process conditions, so an experiment was conducted on the basis of predicted run. Table 9 shows the results of the confirmation experiment using optimal factors. As shown in Table 9, rhamnolipid yield increased from 1.45 to 1.50 g/L, substrate utilization decreased from 26 to 14% (w/v) and lesser biomass, being a side-product, was formed. Overall, the volumetric productivity of the process improved from 0.0086 to 0.0208 g/L/h by 142%. Through this study, it is clearly shown that the multiple performance characteristics are improved.