Abstract:

The effect of dynamic high-pressure microfluidization (DHPM) treatment on activity, stability, and conformation of stem bromelain was studied. Results indicated that bromelain activity was inhibited by DHPM treatment although the residual activity did not decrease with increasing pressure. Under the pressures of 60, 80, 100 MPa and 120 MPa, 94%, 93%, 98% and 92% of bromelain activity were remained, respectively. The optimal temperature of bromelain treated under different pressures exhibited a significant difference, whereas, the optimal pH was not affected. However, DHPM treatments under 60 MPa and 120 MPa resulted in an obvious increase of pH stability. After incubation at pH 8.0 for 40 min, the residual rates of bromelain activity treated under 60 MPa and 120 MPa were 85% and 82%, respectively, which exhibited increases of 14% and 11% compared with untreated bromelain. In addition, conformational change of bromelain induced by DHPM treatment was observed in the change of spectra. Ultraviolet and fluorescence spectra indicated that DHPM treatment induced the unfolding of bromelain and microenvironment changes of tryptophan and tyrosine residues. FTIR spectral analysis indicated that the secondary or tertiary structure of bromelain also disturbed by DHPM.

Key words: dynamic high-pressure microfluidization (DHPM), bromelain, optimal pH, optimal reaction temperature, pH stability, thermal stability, conformation