Enhanced corrosion of 2205 duplex stainless steel by Acetobacter aceti through synergistic electron transfer and organic acids acceleration.

Acetobacter aceti is a microbe that produces corrosive organic acids, causing severe corrosion of industrial equipment. Previous studies have focused on the organic acid corrosion of A. aceti, but neglected the possibility that it has electron transfer corrosion. This study found that electron transfer and organic acids can synergistically promote the corrosion of 2205 duplex stainless steel (DSS). Electrochemical measurement results showed that corrosion of 2205 DSS was more severe in the presence of A. aceti. Surface analysis indicated a thick biofilm formed on the steel surface, with low pH and dissolved oxygen concentrations under the biofilm. Corrosion intensified when A. aceti lacked a carbon source, suggesting that A. aceti can corrode metals by using metallic substrates as electron donors, in addition to its acidic by-products.

Efficient decolorization of melanoidin in raw molasses wastewater by thermophilic esterase in actual extreme conditions.

This work was developed to explore the versatility of thermophilic esterase for decolorizing raw molasses wastewater at high temperature and acidic pH. Combining covalent crosslinking method with deep eutectic solvent, a thermophilic esterase from Pyrobaculum calidifontis was immobilized on chitosan/macroporous resin composite carrier. The application of this immobilized thermophilic esterase eliminated 92.35% of colorants in raw molasses wastewater, achieving maximal decolorization efficiency across all the enzymes tested. Strikingly, this immobilized thermophilic esterase was capable of engaging in continuous activity for a 5-day period while removing 76.23% of pigments from samples. It effectively and continuously eliminated BOD5 and COD, effectively and directly facilitating raw molasses wastewater decolorization under extreme conditions more readily than control group. In addition, this thermophilic esterase was believed to achieve decolorization through an addition reaction that disrupted conjugated system of melanoidins. Together, these results highlight an efficient and practical means of achieving enzyme-based molasses wastewater decolorization.

Theoretical derivation of heuristic molecular lipophilicity potential: a quantum chemical description for molecular solvation.

We present the theoretical derivation of a heuristic molecular lipophilicity potential (HMLP), which gives a structure-based and quantum chemical description of an important aspect of molecular solvation. The quantum mechanical electrostatic potential (ESP) V(r) on a formal molecular surface is calculated, and then the molecular lipophilicity potential L(r) is constructed by comparing the local electron density with the ESP on the surrounding atoms using a screening function. The screening function is derived from statistical mechanical theory treating the polar solvent molecules as dipoles. HMLP is able to describe the main interactions of solute molecules with polar and nonpolar solvent molecules. HMLP is a unified lipophilicity and hydrophilicity potential: its positive values represent lipophilicity, and its negative values represent hydrophilicity. In this paper, several examples show that HMLP gives more reliable descriptions for the molecular solvation than some other methods, such as atomic partial charges and the empirical lipophilicity potential.