Amino-N compounds found in soil organic matter hydrolysates of a loamy sand using an immobilized protease reactor column

Abstract

Soil organic matter (OM) from seven different fertility plots of a loamy sand was extracted and fractionated into high- and low-molecular-weight (HMW, LMW) fractions using gel filtration. The fractions were acid-hydrolyzed to determine the amino sugar and amino acid contents. The same fractions were hydrolyzed with an immobilized protease reactor column. Reverse-phase high-performance liquid chromatography (HPLC) was used to identify the soil amino-N compounds. With the HMW fraction as substrate, the enzyme released less than 1% of 11 amino-N compounds determined by acid hydrolysis. Phenylalanine and leucine, however, were recovered in quantities of 2% and 4%, respectively. Immobilized protease hydrolysis of the LMW fraction recovered considerably more amino-N compounds compared with acid hydrolysis of the same fractions. Each system of hydrolysis produced some amino-N compounds not found in the other. We conclude that an immobilized enzyme reactor column will allow a researcher to perform time-course hydrolysis, so that hydrolysis intermediates, e.g. peptides, can be separated and identified.