A new thermolabile alkaline phospholipase D from Streptomyces sp. CS628

An alkali-tolerant phospholipase D from Sphingobacterium thalpophilum 2015: Gene cloning, overproduction and characterization

The phospholipase pl-S.t gene of Sphingobacterium thalpophilum 2015 was cloned and the gene sequence was submitted to NCBI with Accession Number KX674735.1. The phylogenetic analysis showed that this PL-S.t was clustered to phospholipase D (PLD). As far as we know, the PL-S.t with a molecular mass of 22.5 kDa is the lowest of the currently purified bacterial PLDs, which belongs to a non-HKD PLD enzyme. This PL-S.t was resistant to a wide range of alkali pHs (7.5-9.0) after 1 h incubation, retaining more than 90% of its maximum activity. The PL-S.t activity can be enhanced by Ni²⁺, Co²⁺ and Mn²⁺. This PL-S.t has only one cysteine residue and fewer negatively-charged amino acids (AAs). The hydrogen bonds network was found around the cystein108, which may be beneficial to the stability and activity of PL-S.t in Ni²⁺ solution. This study has laid the foundation for further research on the molecular mechanism of the catalytic characteristics of low molecular weight alkalic PLD from S. thalpophilum 2015.

Immobilization of Phospholipase D on Silica-Coated Magnetic Nanoparticles for the Synthesis of Functional Phosphatidylserine

In this study, silica-coated magnetic nanoparticles (Fe3O4/SiO2) were synthesized and applied in the immobilization of phospholipase D (PLDa2) via physical adsorption and covalent attachment. The immobilized PLDa2 was applied in the synthesis of functional phosphatidylserine (PS) through a transphophatidylation reaction. The synthesis process and characterizations of the carriers were examined by scanning electron microscope (SEM), transmission electron microscope (TEM), and Fourier-transform infrared spectroscopy (FT-IR). The optimum immobilization conditions were evaluated, and the thermal and pH stability of immobilized and free PLDa2 were measured and compared. The tolerance to high temperature of immobilized PLDa2 increased remarkably by 10°C. Furthermore, the catalytic activity of the immobilized PLDa2 remained at 40% after eight recycles, which revealed that silica-coated magnetic nanoparticles have potential application for immobilization and catalytic reactions in a biphasic system.

A novel cold-adapted lipase, LP28, from a mesophilic Streptomyces strain

Fossil fuel is limited but its usage has been growing rapidly, thus the fuel is predicted to be completely running out and causing an unbearable global energy crisis in the near future. To solve this potential crisis, incorporating with increasing environmental concerns, significant attentions have been given to biofuel production in the recent years. With the aim of isolating a microbial biocatalyst with potential application in the field of biofuel, a lipase from Streptomyces sp. CS628, LP28, was purified using hydroxyapatite column chromatography followed by a gel filtration. Molecular weight of LP28 was estimated to be 32,400 Da by SDS-PAGE. The activity was the highest at 30 °C and pH 8.0 and was stable at pH 6.0-8.0 and below 25 °C. The enzyme preferentially hydrolyzed p-nitrophenyl decanoate (C10), a medium chain substrate. Furthermore, LP28 non-specifically hydrolyzed triolein releasing both 1,2- and 1,3-diolein. More importantly, LP28 manifestly catalyzed biodiesel production using palm oil and methanol; therefore, it can be a potential candidate in the field of biofuel.

A novel alkaline lipase from Ralstonia with potential application in biodiesel production

With the aim of isolating a biocatalyst able to catalyze biodiesel production from microbial source, Ralstonia sp. CS274 was isolated and a lipase from the strain (RL74) was purified. Molecular weight of RL74 was estimated to be 28,000 Da by SDS-PAGE. The activity was highest at 50-55°C and pH 8.0-9.5 and was stable at pH 7.0-12.0 and up to 45°C. It was resistant to oxidizing and reducing agents and the activity was enhanced by detergents. RL74 was 1,3 specific and K(m) and V(max) for p-nitrophenyl palmitate were 2.73 ± 0.6mM and 101.4 ± 1.9 mM/min mg, respectively. N-terminal amino acid sequence showed partial homology with that of Penicillium lipases. RL74 produced biodiesel more efficiently in palm oil than in soybean oil; and the production was highest at pH 8.0, at 5% methanol and at 20% water content.