Glycyrrhizin (GL)

the biologically active compounds of liquorice

can be hydrolysed to glycyrrhetic acid 3-O-mono-β-D-glucuronide (GAMG)by whole cells containing β-D-glucuronidase. GAMG is widely used in the pharmaceutical and food industries due to its stronger physiological functions

higher biological activity

more favorable sweetness

and lower caloric value as compared with GL. The recombinant Pichia pastoris (r-PGUS-P)designated in this work expressing β-D-glucuronidase

was used as a whole-cell biocatalyst catalyzing GL to GAMG in non-aqueous solvents systems. The results showed that r-PGUS-P gave the highest yield of GAMG in 1-butyl-3-methylimidazolium hexafluorophosphate (［BMIM］PF6)/water(2∶8

vol)biphasic system. The optimal conditions of this reaction were determined as follows:optimum pH

substrate concentration

temperature and cell content were 5.4

6.0 mmol·L-1

45℃

and 8.0 g·L-1

respectively. Under these optimized conditions

69.6% yield of GAMG and 67.2% of the chemical bond selectivity was achieved after 58 h reaction time

increase by 12.4% and 12.61%

respectively against aqueous phase.  Simultaneously

the ionic liquid ［BMIM］PF6 alsoremained at higher recovery percentage of about 93.47% during repeated use for 7 reaction cycles. Especially

product GAMG and byproduct glycyrrhetinic acid (GA)got separated in biphasic system automatically that brought convenience for the separation and purification of GAMG.