Enhanced human lysozyme production by Kluyveromyces lactis K7 in biofilm reactor coupled with online recovery system

• The recovery conditions of produced human lysozyme were evaluated.
• The best adsorption was obtained at 25 °C, pH 4, and 25% silicic acid ratio.
• The best desorption were determined at 25 °C, pH 6.2.
• Four repetitive desorption process provided up to 98% desorption.
• The online recovery system improved the human lysozyme production (280.4 U/mL).

Kluyveromyces lactis K7 is a genetically modified microorganism, which is proposed to produce the human lysozyme commercially. Up to now, human lysozyme production with this strain was improved by the application of biofilm reactor with plastic composite supports compared to the suspended-cell bioreactor. The goal of this study was to further enhance the human lysozyme production with a simultaneous fermentation in biofilm reactor and online recovery system. For the adsorption of human lysozyme, various percent ratios (wt/v) of silicic acid: fermentation broth as the absorbent, temperature, and pH of the fermentation broth were evaluated, whereas temperature, pH, sodium dodecyl sulfate, NaCl, and ethanol concentrations in the eluent were evaluated for the desorption of the human lysozyme from absorbent. The results demonstrated that the best adsorption (95.6% adsorption) was obtained at 25 °C, pH 4, and 25% silicic acid: fermentation broth volume ratio and the best desorption parameters were determined as 25 °C, pH 6.2, and 5% (wt/v) sodium dodecyl sulfate with 1 M NaCl and 20% (v/v) ethanol as eluent among tested variables. Four repetitive desorption process yielded up to 98% desorption. Finally, the simultaneous fermentation and online recovery system improved the production of human lysozyme to 280.4 U/mL, which is a 63% improvement compared to the biofilm bioreactor without the online recovery system. Therefore, this approach is not only enhanced the human lysozyme production, but also allowed the recovery process simultaneously with fermentation.