Hybridoma-derived neutralizing monoclonal antibodies against Beta and Delta variants of SARS-CoV-2 in vivo.

Neutralizing monoclonal antibodies (mAb) are a major therapeutic strategy for the treatment of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection. The continuous emergence of new SARS-CoV-2 variants worldwide has increased the urgency for the development of new mAbs. In this study, we immunized mice with the receptor-binding domain (RBD) of the SARS-CoV-2 prototypic strain (WIV04) and screened 35 RBD-specific mAbs using hybridoma technology. Results of the plaque reduction neutralization test showed that 25 of the mAbs neutralized authentic WIV04 strain infection. The 25 mAbs were divided into three categories based on the competitive enzyme-linked immunosorbent assay results. A representative mAb was selected from each category (RD4, RD10, and RD14) to determine the binding kinetics and median inhibitory concentration (IC50) of WIV04 and two variants of concern (VOC): B.1.351 (Beta) and B.1.617.2 (Delta). RD4 neutralized the B.1.617.2 variant with an IC50 of 2.67 â€‹ng/mL; however, it completely lost neutralizing activity against the B.1.351 variant. RD10 neutralized both variants with an IC50 exceeding 100 â€‹ng/mL; whereas RD14 neutralized two variants with a higher IC50 (>1 â€‹mg/mL). Animal experiments were performed to evaluate the protective effects of RD4 and RD10 against various VOC infections. RD4 could protect Adv-hACE2 transduced mice from B.1.617.2 infection at an antibody concentration of 25 â€‹mg/kg, while RD10 could protect mice from B.1.351 infection at an antibody concentration of 75 â€‹mg/kg. These results highlight the potential for future modifications of the mAbs for practical use.

Coupling glucose fermentation and homoacetogenesis for elevated acetate production: Experimental and mathematical approaches.

Homoacetogenesis is an important potential hydrogen sink in acetogenesis, in which hydrogen is used to reduce carbon dioxide to acetate. So far the acetate production from homoacetogenesis, especially its kinetics, has not been given sufficient attention. In this work, enhanced production of acetate from anaerobic conversion of glucose through coupling glucose fermentation and homoacetogenesis is investigated with both experimental and mathematical approaches. Experiments are conducted to explore elevated acetate production in a coupled anaerobic system. Acetate production could be achieved by homoacetogenesis with a relative high acetate yield under mixed fermentation conditions. With the experimental observations, a kinetic model is formulated to describe such a homoacetogenic process. The maximum homoacetogenic rate (k(m,homo)) is estimated to be 28.5 ± 1.7 kg COD kg⁻¹ COD day⁻¹ with an uptake affinity constant of 3.7 × 10⁻5± 3.1 × 10⁻6kg COD m⁻³. The improved calculation of homoacetogenic kinetics by our approach could correct the underestimation of homoacetogenesis in anaerobic fermentation processes, as it often occurs in these systems supported by literature analysis. The model predictions match the experimental results in different cases well and provide insights into the dynamics of anaerobic glucose conversion and acetate production. Furthermore, acetate production via homoacetogenesis increases by about 40% through utilizing the fed-batch coupling system, attributed to a balance between the hydrogen production in the acetogenesis phase and the hydrogen consumption in the homoacetogenesis phase. This work provides an effective way for increased anaerobic acetate production, and gives us a better understanding about the homoacetogenic kinetics in the anaerobic fermentation process.

Acetate yield increased by gas circulation and fed-batch fermentation in a novel syntrophic acetogenesis and homoacetogenesis coupling system.

Gas circulation and fed-batch fermentation were applied for enhancing acetate production by mixed culture in a novel syntrophic acetogenesis and homoacetogenesis coupling system. The results show that the acetate yield in the fed-batch test with gas circulation is about 47% higher than that in the batch test without gas circulation. The fed-batch method helps to increase acetate yield by balancing hydrogen production in the acetogenesis phase (the 1st phase) and hydrogen consumption in the homoacetogenesis phase (the 2nd phase) of the coupling system. Gas circulation enhances mass transfer between different phases of the coupling system, hence resulting in increased homoacetogenesis in the 2nd phase and relief of the products (H2) inhibition to syntrophic acetogenesis in the 1st phase. The effects of gas circulation and fed-batch fermentation on direct glucose conversion to acetate were also investigated.

[Acetate production by acidification-homoacetogenesis two-phase coupling process: effect of initial pH].

The effect of initial pH values on acetate production was studied in the acidification-homoacetogenesis two-phase coupling system using glucose as the substrate and the heat-treated and activated anaerobic sludge as the inoculum. Substrate degradation, product yield and pH variation during fermentation were examined at various initial pH values (5, 6, 7, 8, 9, 10 and 11). The results show that initial pH values affect volatile fatty acids and ethanol production not only in the acidification phase itself but also in the homoacetogenesis phase. Ethanol-type fermentation mainly takes place at initial pH 5 while butyrate-type fermentation at initial pH 6 and 7. But acetate is the dominant product at initial pH 8-11. The optimal initial pH value is 10 for acetate production in the two-phase coupling system. At initial pH 8-11, ethanol concentration is highest at the beginning of acidification, but there is a subsequent decline as ethanol is converted to acetate as a result of further metabolism of the microbes.