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.

Influence of ozonolysis time during sugarcane pretreatment: Effects on the fiber and enzymatic saccharification.

Modifications in sugarcane bagasse (SCB) from ozonolysis (O) NaOH (B) and ultrasound (U) (OBU) treatment for cellulosic ethanol production by enzymatic hydrolysis, were evaluated when increasing the exposure time of SCB to ozone. The lignin, cellulose, and hemicellulose after treatment were quantified: lignin removal and a consequent increase in cellulose content were shown using an infrared spectroscopic technique (ATR-FTIR) and chemical characterization. X-ray diffraction analysis (XRD) proved that OBU treatment does not affect the crystalline cellulose portion and electron microscopy techniques established that the fiber region most affected by the OBU treatment was the secondary cell wall, where the greatest lignin content is located. For OBU-60 treatment the lignin content was reduced and consequently there was a significant increase in cellulose content. After enzymatic hydrolysis, this pretreated SCB released 418mgglucose/g, corresponding to six times more than untreated SCB and a yield of 93% of the cellulose available.

Effect of pretreatment and enzymatic hydrolysis on the physical-chemical composition and morphologic structure of sugarcane bagasse and sugarcane straw.

The present work aimed to study the effect of the pretreatment of sugarcane bagasse and straw with microwave irradiation in aqueous and acid glycerol solutions on their chemical composition, fiber structure and the efficiency of subsequent enzymatic hydrolysis. Thermogravimetric analysis showed that the pretreatment acted mainly on the lignin and hemicellulose fractions of the bagasse, whereas, in the straw, lesser structural and chemical changes were observed. The images from transmission electron microscopy (TEM) revealed that treating bagasse and straw with acid glycerol solution loosened the cell walls and there was a breakdown in the pit membrane. The treated material was submitted to hydrolysis for 72h and higher yields of reducing sugars were observed compared to the untreated material (250.9mg/g from straw and 197.4mg/g from bagasse). TEM images after hydrolysis confirmed the possible points of access of the enzymes to the secondary cell wall region of the pretreated biomass.

Ozonolysis combined with ultrasound as a pretreatment of sugarcane bagasse: Effect on the enzymatic saccharification and the physical and chemical characteristics of the substrate.

Sugarcane bagasse (SCB) was treated in three stages using ozone oxidation (O), washing in an alkaline medium (B) and ultrasonic irradiation (U). The impact of each pretreatment stage on the physical structure of the SCB was evaluated by its chemical composition, using an infrared technique (FTIR-ATR), and using thermogravimetric analysis (TGA/DTG). The pretreatment sequence O, B, U provided a significant reduction of lignin and hemicellulose, which was confirmed by changes in the absorption bands corresponding to these compounds, when observed using infrared. Thermogravimetric analysis confirmed an increased thermal stability in the treated sample due to the removal of hemicellulose and extractives during the pretreatment. This pretreatment released 391mg glucose/g from treated SCB after the enzymatic hydrolysis, corresponding to a yield of 94% of the cellulose available.