Valorizing Assorted Logging Residues: Response Surface Methodology in the Extraction Optimization of a Green Norway Spruce Needle-Rich Fraction To Obtain Valuable Bioactive Compounds.

During stemwood harvesting, substantial volumes of logging residues are produced as a side stream. Nevertheless, industrially feasible processing methods supporting their use for other than energy generation purposes are scarce. Thus, the present study focuses on biorefinery processing, employing response surface methodology to optimize the pressurized extraction of industrially assorted needle-rich spruce logging residues with four solvents. Eighteen experimental points, including eight center point replicates, were used to optimize the extraction temperature (40-135 °C) and time (10-70 min). The extraction optimization for water, water with Na2CO3 + NaHSO3 addition, and aqueous ethanol was performed using yield, total dissolved solids (TDS), antioxidant activity (FRAP, ORAC), antibacterial properties (E. coli, S. aureus), total phenolic content (TPC), condensed tannin content, and degree of polymerization. For limonene, evaluated responses were yield, TDS, antioxidant activity (CUPRAC, DPPH), and TPC. Desirability surfaces were created using the responses showing a coefficient of determination (R2) > 0.7, statistical significance (p ≤ 0.05), precision > 4, and statistically insignificant lack-of-fit (p > 0.1). The optimal extraction conditions were 125 °C and 68 min for aqueous ethanol, 120 °C and 10 min for water, 111 °C and 49 min for water with Na2CO3 + NaHSO3 addition, and 134 °C and 41 min for limonene. The outcomes contribute insights to industrial logging residue utilization for value-added purposes.

Effect of ionic liquid on diffusion in P123 gel: fluorescence correlation spectroscopy.

The effect of two room-temperature ionic liquids (RTILs) on the diffusion of three fluorescent dyes in the gel phase of a triblock copolymer, (PEO)(20)-(PPO)(70)-(PEO)(20) [Pluronic P123; poly ethylene oxide (PEO), poly propylene oxide (PPO)], was studied by using fluorescence correlation spectroscopy (FCS). We used three dyes, 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM), coumarin 480 (C480), and coumarin 343 (C343). By field-emission scanning electron microscopy (FESEM), it was observed that the macroscopic structure of the P123 gel remained unaffected upon addition of RTIL. In the absence of RTIL, the diffusion coefficient (D(t)) of the hydrophobic dye DCM (1 µm(2) s(-1) at the core) is smaller than that of the other two hydrophilic dyes (7 µm(2) s(-1) for C480 and C343). On addition of RTIL, the D(t) values of all of the dyes increase, indicating a decrease in local viscosity (η(eff)). The η(eff) of the core of the RTIL-P123 gel estimated from the D(t) of DCM is lower than that of both the P123 gel (at the core η=90 cP) and RTIL (η=110 cP). It is shown that the RTIL affects the structure of the gel by modifying the size of the micellar aggregates and by penetrating the core.

Effect of an ionic liquid on the unfolding of human serum albumin: a fluorescence correlation spectroscopy study.

The effect of the room temperature ionic liquid (RTIL) 1-pentyl-3-methyl-imidazolium bromide ([pmim][Br]) on the unfolding of a protein, human serum albumin (HSA), is studied by fluorescence correlation spectroscopy (FCS). The structural fluctuations of the protein exhibit three characteristic time constants, namely, ~3, ~35 and ~260 µs. On addition of the RTIL, the dynamics become slightly slower, with time constants of ~5, ~40 and ~350 µs. The two fast components (3 and 35 µs in the absence of RTIL and 5 and 40 µs in the presence of RTIL) are assigned to chain motion of the protein. The slowest component (260 or 350 µs) may arise from detachment (unbinding) of the non-covalent dye from the protein. In the absence of RTIL--and on addition of guanidinium hydrochloride (GdnHCl)--as the protein unfolds, the contribution of the fastest component increases rapidly from 10% at 1 M to 40% at 6 M, and its time constant decreases from 3 µs to 1 µs. In the presence of RTIL, the addition of GdnHCl causes significant changes in both the structure (CD spectrum) and the time constants of conformational fluctuation. In the presence of the RTIL, the addition of GdnHCl gives rise to a very slow component (1025 µs in 1 M and 560 µs in 6 M GdnHCl). It is proposed that the guanidinium cation (GdnH(+)) repels the imidazolium cation ([pmim](+)) at the protein surface, and this causes a change in the structure and dynamics of the protein. On addition of 6 M GdnHCl, the diffusion coefficient of C153 bound to HSA decreases. The hydrodynamic radius of the denatured protein (in 6 M GdnHCl) is larger than that of the native protein (about 1.75 times in the absence of RTIL and 2.6 times in the presence of RTIL).