pastoris competent cells (Invitrogen, Darmstadt, Germany). Eighty microlitres of P. pastoris cells were mixed with 2.5 μg of linearized recombinant plasmids. The transformation mixture (100 μL) was plated on YPD agar plates supplemented with zeocin (100 μg mL-1) and incubated at 30°C for 4 days. In order to confirm that P. pastoris contained the recombinant plasmid, PCR and sequence analysis were performed as previously described. Production of crude extracellular MCAP For the production of MCAP in P. pastoris, starter cultures of single #selleck chemicals llc randurls[1|1|,|CHEM1|]# colonies of transformants were grown

in 25 mL YPD media in 100 mL shake flasks for 20 h at 30°C. The cultures were inoculated in triplicate in 75 mL YPD in 250 mL shake flasks to a starting OD600 of 0.1. Cultivation was carried out for 4 days. Considering

that glucose concentrations above 40 g L-1 did not show any increase in MCAP activity, enzyme expression was performed in 20 and 40 g L-1 glucose and adjusted to an initial pH of 5.0 and 7 with citric acid. In order to analyze the effect of temperature in the culture medium on MCAP expression, recombinants were grown at 23, 24, 25, 27 and 30°C, at initial pH of 5.0. The supernatant from cultures was taken every 24 h and cells were harvested by centrifugation at 4000 g at 4°C. Thereafter, milk clotting enzyme activity was analyzed in the supernatant broths. The supernatant culture learn more from wild type P. pastoris was used as a negative control. To analyse MCAP production by M. circinelloides, 6 day cultivation was performed in solid-state reactor. The crude extract was obtained according to the method of Areces and coworker [7] and assayed daily in duplicate. The obtained protein was considered as a control reference MCAP. Protein determination The amount of protein in the crude

extract, supernatant broth, as well in the chromatographic fractions was determined according to the Bradford procedure [14] and bovine serum albumin served as a standard (Fischer Scientific, Schwerte, Germany). Chromatographic analysis of MCAP All chromatographic experiments were done find more using an ÄKTA purifier system (GE Healthcare, Munich, Germany). After removal of the cells by centrifugation at 4000 g, 4°C, he MCAP recombinant protein was purified from the supernatant by cation-exchange chromatography using a 5 mL HiTrap SP FF column attached to the ÄKTA purifier. The protein extract was adjusted to pH 3.1 using citric acid, and then a range of 37–48 mL of the mixture was injected to the previously equilibrated column with 50 mM citric acid buffer pH 3.5 and 75 mM NaCl. After washing with the same buffer and 75 mM NaCl, the elution was performed with the same buffer and 200 mM NaCl and step gradient was developed in 5 column volumes with a flow rate of 1 mL min-1. For protein content and milk clotting assays, 2.5 mL of chromatographic fractions were collected and analyzed.