Immobilization of lipases on porous polypropylene: Reduction in esterification efficiency at low loading

Abstract

Rhizomucor miehei, Humicola sp., Rhizopus niveus, and Candida antarctica B lipases were immobilized by physical adsorption onto a macroporous polypropylene support. In an esterification reaction, the enzyme efficiency, and therefore cost-effectiveness, is greatly affected by enzyme loading, with an apparent suppression of efficiency at low lipase loadings for both R. miehei and Humicola sp. lipases. This results in the appearance of a pronounced maximum in the efficiency-loading relationship at approximately 100,000 lipase units (LU)/g for R. miehei lipase (10% of its saturation loading) and at approximately 200,000 LU/g for Humicola sp. lipase (50% of its saturation loading). The other lipases studied do not show similar trends. At low loadings, only a small portion of the surface area is occupied and gives the lipase the opportunity to spread; it is hypothesized that the reduction in efficiency at low loadings is due to a distortion of the active molecular conformation caused by the lipase maximizing its contact with the support as a result of its high affinity for the support surface. The relationship between efficiency and loading was different for each of the lipases studied, which may reflect both differences in the strength of the affinity of the lipase for the support and in the ease at which the molecular conformation of the lipase can be distorted.

Biodiesel: visão crítica do status atual e perspectivas na academia e na indústria

“…156 As atividades catalíticas e outras características das enzimas podem mudar dependendo do tipo de retenção (química ou física), da força da interação entre a enzima e o suporte utilizado que pode, em alguns casos, causar distorções estruturais na proteína. 158 Ainda, a atividade catalítica da enzima em um determinado suporte pode ser alterada, aumentando ou diminuindo devido à fragmentação do suporte pela interação do sistema de agitação e o suporte.…”

Enantioselective transesterification by Candida antarctica Lipase B immobilized on fumed silica

“…These interactions are essentially driven by the net charge difference between the protein and the surface (Cruz et al, 2009;Koops et al, 1999). An important issue associated with the adsorptive immobilization of enzymes is that conformational changes are sometimes observed (Bosley and Peilow, 1997;Koops et al, 1999;Unsworth et al, 2007; der Veen et al, 2007). These conformational changes may modify the native enzyme structure and promote fluctuations in activity at low enzyme loadings (in this work, referred as low nominal surface coverage).…”

“…Immobilization of enzymes on porous and non-porous solid supports has been intensively explored (Long et al, 2007;Persson et al, 2002). The preferred matrices for immobilization include macroporous polypropylene particles (Bosley and Peilow, 1997), hydrophilic silicon wafers (van der Veen et al, 2007), microemulsions and organogels (Zoumpanioti et al, 2008). Additional efforts include improving compatibility with the solvents by chemical modification of the enzymes' surface (Sheldon et al, 2005), protein engineering (Hudson et al, 2005), and co-lyophilization of the enzyme with various adjuvants, such as cyclodextrin (Ghanem, 2003;Mine et al, 2003), inorganic salts (Lindsay et al, 2002(Lindsay et al, , 2004, and crown ethers (Mine et al, 2003;Santos et al, 2001;Secundo et al, 2007).…”

“…These conformational changes may modify the native enzyme structure and promote fluctuations in activity at low enzyme loadings (in this work, referred as low nominal surface coverage). Thus, a large excess of surface area maximizes the interactions of the lipase with the surface, which can result in the above described structural changes and in reduced activity (Bosley and Peilow, 1997;Koops et al, 1999).…”

“…This might be achieved by increasing the presence of neighboring molecules at increased surface coverages (Bosley and Peilow, 1997;Koops et al, 1999;van der Veen et al, 2007). Mass-transfer limitations may start to be significant at multi-layer coverages thereby, potentially leading to reduced apparent activity.…”