Design of a Cyclodextrin Bioproduction Process Using Bacillus pseudofirmus and Paenibacillus macerans

Cyclodextrin (CD) drug delivery systems offer the potential to enhance the desired physicochemical properties and pharmacokinetic parameters of drugs while maintaining their safety. Cyclodextrin-glucosyl-transferase (CGTase) is amongst the most important enzymes used in CD biosynthesis. However, the bioproduction of CDs still faces challenges in terms of optimization and process complexity. This study proposes a novel CD bioproduction system in a batch mode to increase yield and reduce costs. Two bacterial strains were selected: the alkalophilic Bacillus pseudofirmus DSM2517 strain and the neutrophilic Paenibacillus macerans DSM1574 strain. Three different culture media, two temperatures (30 °C and 37 °C), and three scales (shake flasks 20 mL and 100 mL, and bioreactor 3.2 L) were evaluated with respect to bacterial growth kinetics, protein production, and CGTase biosynthesis and activity for β-CD production. Bacterial growth was monitored by measuring optical density (OD600 nm), while CGTase activity was assessed by measuring β-CD production directly in the medium after filtration or in samples after concentration (using a Vivaspin 500® ultrafiltration spin column with a 10 kDa cut-off). β-CD quantification was performed using the phenolphthalein colorimetric method and HPLC. The best conditions for combined growth and protein production, for both microorganisms, in shake flasks were achieved with a medium containing 2% dextrin as the carbohydrate source. Scale-up to the bioreactor displayed improved growth kinetics for both bacteria and higher protein production and CGTase activity for Paenibacillus macerans.