Wastewater from tapioca processing factory containing high COD (11,077-19,083 mg/l), SS (4,180-7,600 mg/l) and low pH (4.33-5.60) still causes heavy pollution to receiving water in South Vietnam. Closing the water circuit in the tapioca industries represents a very attractive option for eliminating pollution problems and the reuse of treated wastewater and solid wastes. The investigated and presently occasionally already implemented system consists of primary sedimentation tank, anaerobic treatment using UASB-reactors, aeration tanks using attached growth reactor and oxidation ponds system. Under laboratory conditions, organic loading rates applied in UASB-reactors are up to 40,35 kg COD/m3.d with treatment efficiency of 90-95%, reducing the COD concentration from up to 13,449 mg/l to 624-780 mg/l. The final effluent COD (sol.) after treatment in the pond system operated at hydraulic retention time of 12-20 days is lower than 10 mg/l. This effluent is suited very well either for use in agriculture or in the factory.

Folk experiences suggest natural products in Tetradium ruticarpum can be effective inhibitors towards diabetes-related enzymes. The compounds were experimentally isolated, structurally elucidated, and tested in vitro for their inhibition effects on tyrosine phosphatase 1B (PTP1B) and α-glucosidase (3W37). Density functional theory and molecular docking techniques were utilized as computational methods to predict the stability of the ligands and simulate interaction between the studied inhibitory agents and the targeted proteins. Structural elucidation identifies two natural products: 2-heptyl-1-methylquinolin-4-one (1) and 3-[4-(4-methylhydroxy-2-butenyloxy)-phenyl]-2-propenol (2). In vitro study shows that the compounds (1 and 2) possess high potentiality for the inhibition of PTP1B (IC50 values of 24.3 ± 0.8, and 47.7 ± 1.1 μM) and α-glucosidase (IC50 values of 92.1 ± 0.8, and 167.4 ± 0.4 μM). DS values and the number of interactions obtained from docking simulation highly correlate with the experimental results yielded. Furthermore, in-depth analyses of the structure–activity relationship suggest significant contributions of amino acids Arg254 and Arg676 to the conformational distortion of PTP1B and 3W37 structures overall, thus leading to the deterioration of their enzymatic activity observed in assay-based experiments. This study encourages further investigations either to develop appropriate alternatives for diabetes treatment or to verify the role of amino acids Arg254 and Arg676.

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