Lipase activity and enantioselectivity of whole cells from a wild-type Aspergillius flavus strain

Free and Substrate-Immobilised Lipases from Fusarium verticillioides P24 as a Biocatalyst for Hydrolysis and Transesterification Reactions

Fungal enzymes are widely used in technological processes and have some interesting features to be applied in a variety of biosynthetic courses. Here, free and substrate-immobilised lipases from Fusarium verticillioides P24 were obtained by solid-state fermentation using wheat bran as substrate and fungal carrier. Based on their hydrolytic and transesterification activities, the lipases were characterised as pH-dependent in both reactions, with higher substrate conversion in an alkaline environment. Thermally, the lipases performed well from 30 to 45 °C, being more stable in mild conditions. Organic solvents significantly influenced the lipase selectivity using different vegetable oils as fatty acid source. Omega(ω)-3 production in n-hexane achieved 45% using canola oil, against ≈ 18% in cyclohexane. However, ω-6 production was preferably produced for both solvents using linseed oil with significant alterations in the yield (≈ 79% and 49% for n-hexane and cyclohexane, respectively). Moreover, the greatest enzyme selectivity for ω-6 led us to suppose a lipase preference for the Sn1 position of the triacylglycerol. Lastly, a transesterification reaction was performed, achieving 90% of ester conversion in 72 h. This study reports the characterisation and use of free and substrate-immobilised lipases from Fusarium verticillioides P24 as an economic and efficient method for the first time.

Studies on the catalytic behavior of a membrane-bound lipolytic enzyme from the microalgae Nannochloropsis oceanica CCMP1779

The catalytic behavior of a membrane-bound lipolytic enzyme (MBL-Enzyme) from the microalgae Nannochloropsis oceanica CCMP1779 was investigated. The biocatalyst showed maximum activity at 50 °C and pH 7.0, and was stable at pH 7.0 and temperatures from 40 to 60 °C. Half-lives at 60 °C, 70 °C and 80 °C were found 866.38, 150.67 and 85.57 min respectively. Thermal deactivation energy was 68.87 kJ mol^-1. The enzyme's enthalpy (ΔΗ*), entropy (ΔS*) and Gibb's free energy (ΔG*) were in the range of 65.86-66.27 kJ mol^-1, 132.38-140.64 J mol^-1 K^-1 and 107.80-115.81 kJ mol^-1, respectively. Among p-nitrophenyl esters of fatty acids tested, MBL-Enzyme exhibited the highest hydrolytic activity against p-nitrophenyl palmitate (pNPP). The K_m and V_max values were found 0.051 mM and of 0.054 mmole pNP mg protein^-1 min^-1, respectively with pNPP as substrate. The presence of Mn²⁺ increased lipolytic activity by 68.25%, while Fe³⁺ and Cu²⁺ ions had the strongest inhibitory effect. MBL-Enzyme was stable in the presence of water miscible (66% of the initial activity in ethanol) and water immiscible (71% of the initial activity in n-octane) solvents. Myristic acid was found to be the most efficient acyl donor in esterification reactions with ethanol. Methanol was the best acyl acceptor among the primary alcohols tested.

Immobilization of Lipase from Pseudomonas fluorescens on Porous Polyurea and Its Application in Kinetic Resolution of Racemic 1-Phenylethanol

A porous polyurea (PPU) was prepared through a simple protocol by reacting toluene diisocyanate with water in binary solvent of water-acetone. Its amine group was determined through spectrophotometric absorbance based on its iminization with p-nitrobenzaldehyde amines. PPU was then used as a novel polymer support for enzyme immobilization, through activation by glutaraldehyde followed by immobilization of an enzyme, lipase from Pseudomonas fluorescens (PFL), via covalent bonding with the amine groups of lipase molecules. Influences of glutaraldehyde and enzyme concentration and pH in the process were studied. The results revealed that the activity of the immobilized PFL reached a maximum at GA concentration of 0.17 mol/L and at pH 8. Immobilization rate of 60% or higher for PFL was obtained under optimized condition with an enzyme activity of 283 U/mg. The porous structure of PPU, prior to and after GA activation and PFL immobilization, was characterized. The activity of the immobilized PFL at different temperature and pH and its stability at 40 °C as well as its reusability were tested. The immobilized enzyme was finally used as enantioselective catalyst in kinetic resolution of racemic 1-phenylethanol (1-PEOH), and its performance compared with the free PFL. The results demonstrate that the enzyme activity and stability were greatly improved for the immobilized PFL, and highly pure enantiomers from racemic 1-PEOH were effectively achieved using the immobilized PFL. Noticeable deactivation of PFL in the resolution was observed by acetaldehyde in situ formed. In addition, the immobilized PFL was readily recovered from the reaction system for reuse. A total of 73% of the initial activity was retained after 5 repeated reuse cycles. This work provides a novel route to preparation of a polyurea porous material and its enzyme immobilization, leading to a novel type of immobilized enzyme for efficient kinetic resolution of racemic molecules.