High hydrostatic pressure as pretreatment and adjuvant for the enzymatic release of ferulic acid from corn cob

Process Biochemistry

https://doi.org/10.1016/j.procbio.2017.04.011

Bioprocesses based on the use of enzymes can be employed for the obtainment of ferulic acid by its solubilization from corn cob, which is a natural source of this phenolic compound. In order to overcome the limitations caused by the recalcitrance of biomass, the application of pretreatments is advisable. The utilization of high hydrostatic pressure on the enzymatic release of ferulic acid from corn cob with three feruloyl esterase extracts was studied applying pressurization at 600 MPa as a pretreatment in combination with a mild thermal treatment at 130 °C/2 h. Additionally, pressurization at 200 MPa during the enzymatic hydrolysis step was assessed to increase the ferulic acid yield. The results showed that the application of a high pressure pretreatment at 600 MPa/40 °C/15 min to thermally treated corn cob increased by 20% the ferulic acid release in comparison with the thermal treatment for Ultraflo® L, but not for the Aspergillus extracts. Pressurization at 200 MPa during the hydrolysis stage affected differently the enzymes stability and ferulic acid release depending on the extract and the pretreatments applied, showing that the effects of pressurization are complex and must be assessed in each case.

Evaluation of strategies for second generation bioethanol production from fast growing biomass Paulownia within a biorefinery scheme

Applied Energy

http://dx.doi.org/10.1016/j.apenergy.2016.11.114

Fast-growing and short-rotation biomass is identified as glucan-rich feedstock to be used for bioenergy purposes. For the first time to our knowledge, fast growing biomass (Paulownia tomentosa) was evaluated for bioethanol production in a biorefinery scheme. For that, Paulownia wood was subjected to autohydrolysis pretreatment under severity (S0) conditions in the range of 3.31–5.16. The effect of this treatment on its fractionation was evaluated by means of hemicelluloses solubilization as hemicellulose-derived compounds in liquid phase and enzymatic hydrolysis of glucan (remained in the solid phase) into glucose. A xylose and xylooligosaccharides concentration of 17.5 g/L was obtained at S0 = 3.99 which corresponds to complete xylan solubilization. On the other hand, glucose yield of enzymatic hydrolysis increased up to reach 99% at S0 = 4.82. In addition, separate and simultaneous saccharification and fermentation assays (SHF and SSF) of autohydrolyzed Paulownia were compared for ethanol production. An increase of 47% in ethanol concentration was obtained by SHF in comparison with results achieved by SSF for Paulownia treated at S0 = 4.19. In SSF, Paulownia was successfully converted into ethanol (52.7 g/L which corresponded to 80% of ethanol yield) operating at 20% solid loadings and S0 = 4.72. Energy analysis of results obtained in this work showed that 83% of energy respect to raw material can be recovered considering the ethanol and the combustion of residual lignin. This work provides a feasible process for bioethanol production using fast growing specie which could enrich the feedstock needs for biofuels sector.

Structural and thermo-rheological analysis of solutions and gels of a β-lactoglobulin fraction isolated from bovine whey

Food Chemistry, 198 (2016) 45–53

http://dx.doi.org/10.1016/j.foodchem.2015.11.090

A β-Lactoglobulin fraction (r-βLg) was isolated from milk whey hydrolysates produced with cardosins from Cynara cardunculus. The impact of the technological process on the r-βLg structure and how in turn this determined its heat-induced gelation was investigated. Results were analysed taking pure β-Lg (p-βLg) as control sample. The process induced changes in the r-βLg native conformation causing exposure of hydrophobic groups, lower thermal stability and also, shorter thermal treatments needed to give rise to non-native and aggregated species.

At pH 3.2, r-βLg and p-βLg solutions exhibited two gelation steps, with the advantage that r-βLg protein may form stable gels at lower temperature than p-βLg. At pH 7.2, a specific thermo-viscoelastic stability to 73 °C was found, which corresponded to the gel point in both protein solutions. The difference was that while for p-βLg solution in sol state δ < 45° (solid-like), however for r-βLg solution δ > 45° (fluid-like).

Influence of pH on viscoelastic properties of heat-induced gels obtained with a β-Lactoglobulin fraction isolated from bovine milk whey hydrolysates

Food Chemistry, 219, 2017, 169–178

http://dx.doi.org/10.1016/j.foodchem.2016.09.137

A β-Lactoglobulin fraction (r-βLg) was isolated from whey hydrolysates produced with cardosins from Cynara cardunculus. The impact of the hydrolysis process on the r-βLg structure and the rheological properties of heat-induced gels obtained thereafter were studied at different pH values. Differences were observed between r-βLg and commercial β-Lg used as control. Higher values for the fluorescence emission intensity and red shifts of the emission wavelength of r-βLg suggested changes in its tertiary structure and more solvent-exposed tryptophan residues. Circular dichroism spectra also supported these evidences indicating that hydrolysis yielded an intermediate (non-native) β-Lg state.

The thermal history of r-βLg through the new adopted conformation improved the microstructure of the gels at acidic pH. So, a new microstructure with better rheological characteristics (higher conformational flexibility and lower rigidity) and greater water holding ability was founded for r-βLg gel. These results were reflected in the microstructural analysis by scanning electron microscopy.