The gene encoding homodimeric β-galactosidase (lacA) from Bacillus licheniformis DSM 13 was cloned and overexpressed in Escherichia coli, and the resulting recombinant enzyme was characterized in detail. The optimum temperature and pH of the enzyme, for both o-nitrophenyl-β-D: -galactoside (oNPG) and lactose hydrolysis, were 50°C and 6.5, respectively. The recombinant enzyme is stable in the range of pH 5 to 9 at 37°C and over a wide range of temperatures (4-42°C) at pH 6.5 for up to 1 month. The K(m) values of LacA for lactose and oNPG are 169 and 13.7 mM, respectively, and it is strongly inhibited by the hydrolysis products, i.e., glucose and galactose. The monovalent ions Na(+) and K(+) in the concentration range of 1-100 mM as well as the divalent metal cations Mg²(+), Mn²(+), and Ca²(+) at a concentration of 1 mM slightly activate enzyme activity. This enzyme can be beneficial for application in lactose hydrolysis especially at elevated temperatures due to its pronounced temperature stability; however, the transgalactosylation potential of this enzyme for the production of galacto-oligosaccharides (GOS) from lactose was low, with only 12% GOS (w/w) of total sugars obtained when the initial lactose concentration was 200 g/L.

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Total and soluble oxalate content levels were measured in thirteen selected vegetables purchased from a local market in Surin Province in the northeast of Thailand. Total oxalate contents of the leaves, shoots and roots of the fresh vegetables ranged from 249.5 ± 12.1 to 7597.9 ± 77.6 mg oxalate/100g dry matter (DM) while soluble oxalate content ranged from 205.0 ± 2.3 to 2677.6 ± 19.0 mg oxalate/100g DM. Very high levels of total oxalates were found in three of the selected Thai vegetables, Polygonum odoratum (7597.9 ± 77.6 mg/100g DM), Piper aurantaucum (7026.6 ± 76.9 mg/100g DM) and Limnophila aromatica (6179.0 ± 23.6 mg/100g DM). However, the soluble oxalate content of L. aromatica was low and the highest soluble oxalate contents of fresh vegetables were found in P. odoratum, P. aurantuacum and Neptunia oleracea at 2677.6 ± 19.0, 2152.2 ± 65.3 and 1640.8 ± 3.4 mg/100g DM, respectively. Boiling the vegetables reduced the soluble oxalate content between 30.4 and 65.0%. The insoluble oxalate levels increased in eleven of the cooked vegetables while small decreases were observed in L. aromatica and N. oleracea.