Analysis of a thermostable lipase from CTG-clade yeast: Molecular expression, characterization and structure prediction

Aims@#This study was aimed to express Meyerozyma guilliermondii strain RT lipase using Komagataella phaffii X-33 expression system and its biochemical characterization and analyse the predicted structure of the product.@*Methodology and results@#Meyerozyma guilliermondii strain RT obtained from the previous study was used as the source of RT lipase gene. Extracellular M. guilliermondii strain RT lipase expression has significantly been improved up to 56 U/mg at 24 h cultivation in Yeast extract-Peptone-Dextrose (YPD) medium containing (in w/v): 1% yeast extract, 2% peptone, 2% dextrose with 0.5% v/v methanol induction. Characterization of RT lipase showed optimum activity at 45 °C and pH 9. It exhibited stability in the alkaline pH range (8 to 10) and retained 50% of its residual activity at 30 °C for 30 min. Substrate specificity analysis revealed that it preferred short to medium-chain triacylglycerols (C2-C12) with the highest activity towards caprylic acid (C8). Pairwise alignment revealed three substitutions (S2L, S92L and S193L) present in non-CTG-clade hosts (K. phaffii). Homology modelling (YASARA) was used to predict the structures of RT lipase [wild type (wt) and recombinant (rc)]. Mutational analysis of the structures showed the differences in loops that might attribute to the reduction of the optimum temperature from 75 °C (wt) to 45 °C (rc).@*Conclusion, significance and impact of study@#RT lipase was successfully overexpressed extracellularly using K. phaffii expression system with 91.8-fold higher specific activity than the native host. The conceptual advances on the importance of codon optimization before expressing a protein from a CTG-clade species in a non-CTG-clade yeast have been highlighted and the effect of the rare codon usage in recombinant protein characteristics has been evident.

Milk-deteriorating exoenzymes from Pseudomonas fluorescens 041 isolated from refrigerated raw milk

The practice of refrigerating raw milk at the farm has provided a selective advantage for psychrotrophic bacteria that produce heat-stable proteases and lipases causing severe quality problems to the dairy industry. In this work, a protease (AprX) and a lipase (LipM) produced by Pseudomonas fluorescens 041, a highly proteolytic and lipolytic strain isolated from raw milk obtained from a Brazilian farm, have been purified and characterized. Both enzymes were purified as recombinant proteins from Escherichia coli. The AprX metalloprotease exhibited activity in a broad temperature range, including refrigeration, with a maximum activity at 37 °C. It was active in a pH range of 4.0 to 9.0. This protease had maximum activity with the substrates casein and gelatin in the presence of Ca+2. The LipM lipase had a maximum activity at 25 °C and a broad pH optimum ranging from 7.0 to 10. It exhibited the highest activity, in the presence of Ca+2, on substrates with long-chain fatty acid residues. These results confirm the spoilage potential of strain 041 in milk due to, at least in part, these two enzymes. The work highlights the importance of studies of this kind with strains isolated in Brazil, which has a recent history on the implementation of the cold chain at the dairy farm.

Production and characterization of an extracellular lipase from Candida guilliermondii

Extracellular lipases from the endophytic yeast Candida guilliermondii isolated from castor leaves (Ricinus communis L.) were produced using low-cost raw materials such as agro-industrial residues and applying them in the esterification of oleic acid for evaluating their potential use in biodiesel production. After partial purification using ammonium sulfate, the enzyme was characterized and presented higher activity (26.8 ± 1.5 U mL-1) in the presence of 5 mmol L-1 NaCl at 30 ºC and pH 6.5. The production through submerged fermentation was formerly performed in 150 mL erlenmeyer flasks and, once the enzyme production was verified, assays in a 14 L bioreactor were conducted, obtaining 18 ± 1.4 U mL-1. The produced enzyme was applied in the oleic acid esterification under different solvents: hexane, cyclohexane or cyclohexanone) and different acid:alcohol molar ratios. Higher ester conversion rate (81%) was obtained using hexane and the molar ratio of 1:9 was the best conditions using methanol. The results suggest the potential for development of endophytic yeast in the production of biocatalyst through submerged fermentation using agroindustrial residues as culture medium.

Isolation and characterization of novel thermophilic lipase-secreting bacteria

The purpose of the present study was to screen and identify the lipase-producing microorganisms from various regions of Iran. Samples collected from hot spring, Persian Gulf, desert area and oil-contaminated soil, were analyzed for thermophilic extracellular-lipase producing organisms. Six strains with high activity on rhodamine B plates were selected for chemical identification and further study. Among these isolated bacteria, four strains show higher activity in pH-Stat method at 55 °C. These strains were identified by PCR amplification of 16s rRNA genes using universal primers. Fermentation increased the activity up to 50%. The growth medium, designed for lipase production, increased the activity up to 4.55 folds. The crude supernatant of ZR-5 after fermentation and separation the cells, was lyophilized and the activity was measured. Total activity of this strain was 12 kU/g that shows its potential for industrial uses. Further study is required for purification of enzyme and calculation its specific activity. Immobilization is another approach should be considered.

Microbial lipases: production of extracellular lipase enzyme by alcaligenes viscosus (Doge-1) strain.

Industrially important extracellular lipase enzyme production was explored by utilizing microbial strain isolated from dairy effluents. Alcaligenes viscosus DOGE-1 strain isolated from dairy waste waters proved to produce extracellular lipase. Various growth factors were attempted to maximize the lipase production by this strain. Growth factors like NH4PO4, Peptone, Urea coupled with peptone, KH2PO4, Olive oil and pH were found to be favored the maximum lipase production. This microbial strain was found to have a high lipolytic activity.