Significantly enhanced enzymatic hydrolysis of waste rice hull through a novel surfactant-based deep eutectic solvent pretreatment.

The potential of green solvents, specifically deep eutectic solvents (DESs), has piqued the interest of researchers in the field of lignocellulose pretreatment. To enhance the enzymatic digestion efficiency of waste rice hull (RCH), an effective pretreatment approach was developed using the DES [AA][CATB], which was made with acetic acid (AA) and cetyltrimethylammonium bromide (CTAB). The results showed that [AA][CATB] improved enzymatic saccharification by 3.7 times compared to raw RCH and efficiently eliminated lignin and removed xylan. The improvement in enzymatic hydrolysis efficiency was then interpreted by a series of characterizations that showed a great morphological changed RCH with an obvious accessibility increase and a lignin surface area and hydrophobicity reduction. This work demonstrates that functional, and easily recoverable DESs have potential for improving the efficiency of lignocellulose pretreatment in biorefineries, providing a promising approach for developing green solvents and achieving more sustainable and efficient biorefinery processes.

The copper(II) complex of dantron showed therapeutic effect on bacterial gill-rot disease in tilapia infected by Flavobacterium columnar.

Dantron (DA), a kind of polyhydric anthraquinone and one of the bio-active ingredient in Rheum officinale was chosen as the ligand to coordinate with the bio-active copper(II) ion to achieve its antibacterial copper(II) complex, DA-Cu. The coordination structure of DA-Cu, both in the crystal state and solution state, was studied by spectroscopy and X-ray single-crystal diffraction analysis. The inhibition zone, MIC (minimum inhibitory concentration) and MBC (minimum bactericidal concentration) values regarding the in vitro antibacterial activity of DA-Cu towards Flavobacterium columnar, which causes the bacterial gill-rot disease on fish, were significant and specific. DA-Cu in vivo acute toxicity on zebrafish and tilapia was evaluated, suggesting that the higher dose of DA-Cu than 0.1 mg/mL might give potential toxicity. The further therapeutic effect of DA-Cu on the tested tilapia challenged by Flavobacterium columnar was also studied, which showed its clear advantage (including the survival rate, relative weight gain rate, and feed conversion ratio) over DA and the positive control, Sanhuang San, at a much lower dosage of 0.025 mg/mL.

A New Calcium(II)-Based Substitute for Enrofloxacin with Improved Medicinal Potential.

Enrofloxacin (EFX) reacting with Ca(II) afforded a new complex, [Ca(EFX)2(H2O)4] (EFX-Ca), which was structurally characterized both in solid and solution chemistry. E. coli and S. typhi were tested to be the most sensitive strains for EFX-Ca. The LD50 value of EFX-Ca in mice was 7736 mg/kg, implying the coordination of EFX to Ca(II) effectively reduced its acute toxicity. EFX-Ca also decreased the plasma-binding rate and enhanced the drug distribution in rats along with longer elimination half-life. EFX-Ca also showed similar low in vivo acute toxicity and higher anti-inflammation induced by H2O2 or CuSO4 in zebrafish, with reactive oxygen species (ROS)-related elimination. The therapeutic effects of EFX-Ca on two types (AA and 817) of E. coli-infected broilers were also better than those of EFX, with cure rates of 78% and 88%, respectively. EFX-Ca showed promise as a bio-safe metal-based veterinary drug with good efficacy and lower toxicity.

A new calcium(II) complex of marbofloxacin showing much lower acute toxicity with retained antibacterial activity.

Marbofloxacin (MB) is a newly developed veterinary drug with broad-spectrum antibacterial activity. In this study, a new calcium(II)-based complex of marbofloxacin, MB-Ca, was synthesized and structurally characterized by IR, ESI-MS, UV-Vis and single crystal X-ray diffraction analysis. The characterization of this complex in solution state indicated that the coordinated MB-Ca was partly retained, along with the monomeric and dimeric forms of MB. It also showed satisfactory water solubility (1.89 mg/mL), comparing with MB (2.82 mg/mL) at 35 °C. The in vitro antibacterial activity of MB-Ca was also screened towards a series of typical pathogenic bacteria, and determined by the methods of turbidimetry and disc diffusion. The results indicated it showed comparable antibacterial activity to MB. However, it exhibited higher inhibitive ability in vitro on DNA gyrase than MB alone. Furthermore, MB-Ca showed significantly lower acute toxicity (LD50, 3186 mg/kg) than MB (LD50, 1294 mg/kg) in mice, based on the in vivo acute toxicity test. The histopathological examination on the major organs of the mice by the oral administration of MB-Ca did not show obvious organic lesions, which is similar to those treated by MB. The research results suggest that MB-Ca could be further developed into a new promising metal-based veterinary drug and a better substitute of MB, showing unabated antibacterial activity along with lower toxicity.