Enzymatic Removal of Phenol and Chlorophenols Using Soybean Seed Hulls

Abstract

Soybean peroxidase (SBP), (EC 1.11.1.7) can be readily extracted from soybean seed hulls. This study reports on the direct use of soybean seed‐hull extracts for the bioremediation of phenolic wastes. The crude SBP extract from the hulls, like pure soybean peroxidase, is catalytically active in a broad range of pH and temperatures. As SBP is gradually released into the aqueous solution from seed hulls, the direct use of soybean seed hulls can reduce SBP inactivation by H2O2 and enhance the utilization efficiency of SBP through the slow release of the enzyme from the seed hulls. However, large doses of soybean seed hulls were found to be ineffective in phenol removal. Gradual additions of H2O2 in combination with the SBP released from the hulls were applied to optimize the bioremediation. Since the crude extract contains a mixture of multiple soybean proteins, soybean seed hull slurry required a higher concentration of H2O2 to remove the phenolic substrates than did the purified enzyme. Under the experimental conditions, 80 % of phenol (10.6 mM), 96 % of 2‐chlorophenol (3.9 mM), 95 % of 2,4‐dichlorophenol (3.1 mM), and 94 % of mixed phenol and chlorophenols were removed using soybean seed hulls in a single batch reactor. These results demonstrate that soybean seed hulls, compared to purified SBP, may be a more cost‐effective alternative in the enzymatic removal of phenolic compounds through polymerization reactions.

Biocatalytic properties of a peroxidase-active cell-free extract from onion solid wastes: caffeic acid oxidation

“…Similar results were reported for SBP, which showed pH optima between 5.5 and 8 when used for the removal of a variety of chlorophenols (Caza et al 1999). By contrast, other investigations indicated that SBP was more effective in removing certain phenols from artificial waste water at pH 9 (Wright andNicell 1999), 8.2 (Kennedy et al 2002) and 7 (Bassi et al 2004). Removal of chlorophenols from model media using TNP and BGP was shown to be optimal within a pH range 5-7 (Duarte-Vázquez et al 2002) and 5-6 (Akhtar and Husain 2006), respectively.…”

Investigation on biocatalytic properties of a peroxidase-active homogenate from onion solid wastes: An insight into quercetin oxidation mechanism

“…Similar results were reported for SBP, which showed pH optima between 5.5 and 8 when used for the removal of a variety of chlorophenols [16]. By contrast, other investigations indicated that SBP was more effective in removing certain phenols from artificial waste water at pH 9 [28], pH 8.2 [19] and pH 7 [32]. Removal of chlorophenols from model media using TNP and BGP was shown to be optimal within a pH range 5-7 [30] and 5-6 [31], respectively.…”

A simple lab-scale extraction of soybean hull peroxidase shows wide variation among cultivars

“…Recombinant protein expression and protein engineering (Asad et al, 2011;Grigorenko et al, 1999;Morawski et al, 2000) have been implemented in some of these cases. For some applications, crude SBP may be sufficient or preferred such as in waste water treatment (Bassi et al, 2004;Flock et al, 1999;Wilberg et al, 2002) or as a biocatalyst in organic synthesis (Bouldin et al, 2011;Velde et al, 2001), whereas higher value commodities such as diagnosis tests and therapeutics would require more costly alternatives such as purified or recombinant peroxidases. HRP and SBP have very similar three-dimensional structure with 57% sequence homology (Kamal and Behere, 2003).…”