Xanthan production on crude glycerol-based medium by local Xanthomonas isolate: Optimization of inoculum incubation time

Abstract

This study is concerned with the optimization of inoculum preparation for xanthan production on crude glycerol-based medium in terms of incubation time of the Xanthomonas strain isolated from infected pepper leaves. Experiments within this research were performed according to 3-level factorial design in order to evaluate the effects of varied parameters, i.e. incubation time of inoculum I (24-48 h) and incubation time of inoculum II (24- 48 h) on xanthan concentration in production medium at the end of bioprocess. Inoculum preparation was performed in two steps (inoculum I and inoculum II) under aerobic conditions, at 25 ?C and 150 rpm. Xanthan biosynthesis was performed at a laboratory level under aerobic conditions at 30 ?C and 150 rpm for 168 h. The quality of the prepared inoculum was assessed indirectly, based on xanthan concentration in the production medium at the end of the bioprocess. Response surface methodology was used to define mathematical model, which describes the individual and interactive effects of examined parameters on the xanthan quantity, while desirability function approach was applied to optimize their values. The obtained results suggest that applied strain is the most productive if the incubation time of inoculum I is between 32 h and 40 h, and the incubation time of inoculum II is in the range from 40 h to 48 h. The developed model predicts that the maximum xanthan concentration of about 10.5 g /L can be achieved if the incubation times of inoculum I and inoculum II are 36 h and 48 h, respectively.