Screening and isolation of alkalophilic cyclodextrin glucanotransferase (CG tase) producing bacteria from soil

Abstract

Sixty soil samples in Khon Kaen University were collected and screened for alkalophilic
CG Tase-producing bacteria. Each soil sample of 1 g was suspended in 9 mL of sterilized water and 0.1 mL
of the suspensions was spread on Horikoshi-II medium agar, pH 10.3, containing 0.03% phenolphthalein and
0.01% methyl orange, and incubated at 37 ^oC for 24-72 h. Yellow zones were observed around the CG Tase-producing colonies due to phenolphthalein inclusion complexes inside cyclodextrin. Five isolates
were selected and further analyzed by cyclodextrin (CD)-trichoroethylene (TCE) assay. The results showed
that isolates # 2, 6, 10, 26 and 37 gave CGTase activities as dilution limit at 1:2⁴, 1:2⁵, 1:2⁶, 1:2³ and 1:2³,
respectively. The cassava starch was the most effective inducer in comparison to other soluble- and potato
starches. The identification of cyclodextrins by paper chromatography indicates that isolates # 2, 26 and 37
produce α-CD and β-CD while isolate # 6 and 10 produce only β-CD.