Ultrafiltration system for cyclodextrin production in repetitive batches by CGTase from Bacillus firmus strain 37

This study aimed to improve the yield of cyclodextrins (CDs) production in repetitive batches. An innovative ultrafiltration system was used to remove the inhibitory products that accumulated in the medium and to recover the enzyme. The assays were performed with the CGTase from Bacillus firmus strain 37 in purified, semi-purified, and crude extract forms. Maltodextrin (10 % w/v) and corn starch (5 % w/v) were used as substrates. After eight repetitive 24-h batches, the yield of β-CD obtained with the purified enzyme and the corn starch substrate was 0.54 mmol/L/h, which was 36 % greater than that observed with the 10 % maltodextrin substrate. The crude CGTase extract with the corn starch substrate showed a productivity of 0.38 mmol/L/h, which was 29 % lower than using the purified enzyme and the corn starch substrate but 7 % higher than using the purified enzyme and the maltodextrin substrate. The crude extract, assayed with the corn starch substrate in the presence of 10 % ethanol reached 0.43 mmol/L/h productivity, which was 12 % higher compared to the assay without ethanol. The semi-purified enzyme was assayed with the corn starch substrate in the presence of 10 % ethanol for eight batches lasting 12 h and an excellent selectivity for the β-CD was obtained, reaching a mean percentage of 96.0 %. Therefore, this ultrafiltration system enabled several batches of CD production, with efficient removal of products inhibitory to the CGTase and recovery of the enzyme. The possibility of industrial application of this system is promising.