The processing of harvested E. coli cell broths is examined where the expressed protein product has been released into the extracellular space. Pre-treatment methods such as freeze–thaw, flocculation, and homogenization are studied. The resultant suspensions are characterized in terms of the particle size distribution, sensitivity to shear stress, rheology and solids volume fraction, and, using ultra scale-down methods, the predicted ability to clarify the material using industrial scale continuous flow centrifugation. A key finding was the potential of flocculation methods both to aid the recovery of the particles and to cause the selective precipitation of soluble contaminants. While the flocculated material is severely affected by process shear stress, the impact on the very fine end of the size distribution is relatively minor and hence the predicted performance was only diminished to a small extent, for example, from 99.9% to 99.7% clarification compared with 95% for autolysate and 65% for homogenate at equivalent centrifugation conditions. The lumped properties as represented by ultra scale-down centrifugation results were correlated with the basic properties affecting sedimentation including particle size distribution, suspension viscosity, and solids volume fraction. Grade efficiency relationships were used to allow for the particle and flow dynamics affecting capture in the centrifuge. The size distribution below a critical diameter dependant on the broth pre-treatment type was shown to be the main determining factor affecting the clarification achieved. Biotechnol. Bioeng. 2014;111: 913–924. © 2013 The Authors. Biotechnology and Bioengineering Published by Wiley Periodicals, Inc.

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An alternative route for the production of polyclonal F(ab')(2) fragments that might be adopted for the facile preparation of antivenoms is assessed in this work. The method involves the digestion of whole serum by free pepsin, which results in reduction of the number of processing steps commonly in use, because it avoids the initial purification of IgG's prior to their proteolytic cleavage by the enzyme. Digestion kinetics of whole serum and caprylic acid prepurified IgG using free pepsin were monitored with SDS-PAGE followed by densitometric analysis and antigen binding activity assay of the digested samples. It was observed that with equal units of pepsin activity, caprylic acid prepurified IgG was digested more rapidly than whole serum but that the overall retention of antigen binding activity was significantly greater in the latter case. The estimated first-order digestion rate parameters were 11.8 and 4.42 microM min(-)(1) for pure IgG and whole serum, respectively. The K(m) value obtained for whole serum digestion was 33 microM and that for pure IgG digestion was 43.5 microM. Calibration with undigested whole serum and pure IgG samples of known concentrations was performed using SDS-PAGE followed by image analysis. A linear relationship was observed between the protein concentration and the respective band intensity within the range of concentrations investigated (0.63-31.2 microM IgG concentration). This technique proved to be relatively rapid, reproducible, and more precise than size-exclusion chromatography as a result of its F(ab')(2)/IgG resolving power. Staining and destaining protocols were reproduced in terms of staining and destaining times, volumes added, and compositions. Furthermore, all digestion experiments were performed in duplicate sets to monitor the extent of variation of the digestion kinetic parameters measured by this method. The results obtained from this technique confirm and quantify previous observations that pepsin digestion of whole serum is slower and easier to control than digestion of pure IgG and results in higher recovery of antigenic binding activity.

The Coronavirus Disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has triggered an international pandemic that has led to significant public health problems. To date, limited evidence exists to suggest that drugs are effective against the disease. As possible treatments are being investigated, herbal medicines have shown potential for producing novel antiviral agents for the COVID-19 disease. Aim This review explored the potential of Malawi’s traditional medicinal plants for the management of COVID-19. MethodsThe authors searched on PubMed and Google scholar for medicinal plants that are used in Malawi and published in openly available peer reviewed journals. Plants linked with antiviral treatment, anti-COVID-19 activity or COVID-19 symptoms management were targeted. These included activity against pneumonia, inflammation, cough, difficulty in breathing, pain/aches, fever, diarrhoea, rheumatism, fatigue, asthma, immunocompromised and cardiovascular diseases.Results11 studies were found with 306 plant species. 127 plant species had at least one COVID-19 related pharmacological activity. Of these plant species, the number of herbal entities used for each indication was: pain/aches (87), fever (2), pneumonia (9), breathing/asthma problems (5), coughing (11), diarrhoea (1), immunosuppression (8), blood issues (10), fatigue (2), heart problems (11), inflammation (8), rheumatism (10) and viral diseases (12). Thirty (30) species were used for more than one disease and Azedarachta indica topped the list (6 of the 13 COVID-19 related diseases). The majority of the species had phytochemicals known to have antiviral activity or mechanisms of actions linked to COVID-19 and consequent diseases’ treatment pathways.ConclusionMedicinal plants are a promising source of compounds that can be used for drug development of COVID-19 related diseases. This review highlights potential targets for the World Health Organization and other research entities to explore in order to assist in controlling the pandemic.

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