Raman Spectroscopy Study Structural Changes in Black Bean Protein Isolate upon Ultrasonic-Treatment.

This article focused on the assessment of the potential of Raman spectroscopy for the determination of structural changes in black-bean protein isolate (BBPI) dispersions with low-frequency (20 kHz) ultrasonication applied at various powers (150, 300 or 450 W) and for different durations (12 or 24 min). It also reported on differential scanning calorimetry analyses. A decrease in TD at low- and medium-power ultrasonication confirmed these ultrasonication treatment disrupted internal hydrophobic interactions of protein molecules and broke up unstable aggregates to smaller soluble protein aggregates, while an increase in TD at high-power was attributed to repolymerization of aggregates. Raman spectroscopy analysis revealed a decrease in the α-helix proportion and an increase in ß-sheets after ultrasonic treatment except Sample E (300 W, 24 min). Transformation of aggregation results in a reconstruction in secondary structure of BBPI, especially in ß-sheet structure. Ultrasonic-treatment induced a decrease in the normalized intensity of the Raman band near 760 cm-1 which indicated that Tryptophan residues tended to expose and also indicated protein partially unfolding. No significant difference was found in Tyr doublet ratios between unheated and ultrasound-treated BBPI indicated that ultrasound did not change the microenvironment around tyrosyl residues. While the intensity of 1 450 cm-1 band increased with increasing ultrasonic intensity and treatment time, and then decreased with further increase in power and treatment time. In general, the formation of aggregation transferred g-g-t conformation to t-g-t conformation. Though some mechanism of aggregation-repolymerization of BBPI remains to be clearly defined, Raman spectroscopy provide a feasible tool to study the structural changes of BBPI prepared under different ultrasonic conditions, give a new perspective to elucidation of protein structure.

Unravelling the influence of sulfate loading on enhancing anaerobic co-digestion of corn stover and bio-kerosene production wastewater.

This study was conducted to investigate the effect of sulfate loading on methane production and organic matter degradation during the mesophilic anaerobic co-digestion of corn stover and bio-kerosene production wastewater (BKPW). The highest methane production of 192.04 mL/gVS was obtained at a sulfate concentration of 86 mg/L. This was 46.80% higher than that achieved by a sulfate concentration of 113 mg/L. Additional degradation of organic matter was obtained at a sulfate concentration of 113 mg/L because organic matter in the corn stover and BKPW was oxidized by sulfate-reducing bacteria (SRB). The concentration of sulfate declined by approximately 23% after 29 days of anaerobic co-digestion, and this reduction in sulfate was enhanced when the soluble chemical oxygen demand (SCOD)/sulfate ratio was less than 15. The results of a mass balance analysis showed that 34.87% of C element and 10.04% of S element in substrate, respectively, were converted to biogas during anaerobic co-digestion of corn stover and BKPW at a sulfate concentration of 86 mg/L. The microbial community was analysed using 16S rDNA sequencing technology, and the results showed that the relative abundance of Synergistes (related to methane production with acetic acid) at a sulfate concentration of 86 mg/L had obviously increased and was approximately 287% higher than the abundance achieved at a sulfate concentration of 113 mg/L.

Soy Protein Isolate-Phosphatidylcholine Nanoemulsions Prepared Using High-Pressure Homogenization.

The nanoemulsions of soy protein isolate-phosphatidylcholine (SPI-PC) with different emulsion conditions were studied. Homogenization pressure and homogenization cycle times were varied, along with SPI and PC concentration. Evaluations included turbidity, particle size, ζ-potential, particle distribution index, and turbiscan stability index (TSI). The nanoemulsions had the best stability when SPI was at 1.5%, PC was at 0.22%, the homogenization pressure was 100 MPa and homogenization was performed 4 times. The average particle size of the SPI-PC nanoemulsions was 217 nm, the TSI was 3.02 and the emulsification yield was 93.4% of nanoemulsions.