Screening and optimization of cyclodextrin glucanotransferase production by an alkaliphile Paenibacillus daejeonensis P-83

Cyclodextrin glucanotransferase (CGTase, EC 2.4.1.19) is the member of starch degrading enzymes that catalyses an intramolecular transglycosylation reaction to produce cyclodextrins. CGTase producing 141 isolates were obtained from different agricultural fields (paddy, corn, potato, sorghum, and millet), gardens, and industrial waste soil samples. Amongst these 141, an alkaliphilic CGTase producing bacterial isolate Paenibacillus daejeonensis P-83 was selected. Although the CGTase showed the ability to produce α-, β-, and γ-cyclodextrins, the optimization studies were focused on β-CD production. One-factor-at-a-time (OFAT) increased the initial CGTase production from 1.05 U/ml to 2.76 U/ml with optimal conditions like, 3 % (w/v) water chestnut flour, 0.5 % (w/v) peptone, 0.5 % (w/v) yeast extract, 0.02 % (w/v) MgSO 4 , 0.1 % (w/v) K 2 HPO 4 , pH 11 ± 0.2, 6 % (v/v) inoculum, and incubation at 30 °C ± 0.2 for 72 hours on a rotary shaker (150 rpm). The CGTase production was increased upto 5.23 U/ml by statistical optimization via Central Component Design (CCD) using three variables i.e., water chestnut flour (3.65 %; w/v), peptone (1.1 %; w/v), and yeast extract (0.5 %; w/v). The optimization process significantly increased the CGTase production by 2.55 and 4.9 times using OFAT and CCD, respectively. • A potential CGTase producing bacterial isolate Paenibadcillus daejeonensis P-83 was isolated from millet farm soil sample. • This P. daejeonensis P-83 CGTase was able to produce three types of cyclodextrins (α, β, and γ). • The optimization of CGTase production using OFAT and CCD resulted into about five times increased enzyme. • A raw starch substrate, water chestnut flour was found as the best low-cost carbon source for higher CGTase production.