Statistical optimization of immunoaffinity purification of hepatitis B surface antigen using response surface methodology

Diamond in the rough: Polishing waste polyethylene terephthalate into activated carbon for CO2 capture

The scientific community has believed the potential of waste PET plastics as an effective carbon precursor, however, developing PET-derived activated carbons (PETACs) for a specific application is still a challenge we are facing. To overcome the limitation, a whole chain from development method screening to experiments design, finally to sample optimization, for a sample with promising performance, is proposed in this work. By employing PETACs as CO₂ adsorbents, the waste PET plastics, which we believed the "diamond in the rough", have been polished successfully. Therewith the problems of plastic pollution and the greenhouse effect could be simultaneously solved. The first half part of this paper is a mini review: the PETACs development methods were reviewed and the most suitable solution to develop CO₂ adsorbent, i.e., the two-step chemical activation method, was selected. In addition to that, the necessary procedure variables and their value range were determined. In the second half part, the central composite design method was applied for experiments design in which the procedure variables obtained were regarded as the independent indicators (factors here) while the performance indicators, including yield, CO₂ adsorption uptake, and CO₂ over N₂ selectivity, were treated as the dependent indicators (responses here). The responses were obtained through the characterization of the samples developed and statistical analysis could be applied to reveal the relations between the factors and responses. A high-value PETAC, P600K600-1.5, with the highest gas selectivity (22.189) and decent CO₂ adsorption uptake (3.933 mmol/g) was successfully designed.

A novel application of ion exchange chromatography in recombinant hepatitis B vaccine downstream processing: Improving recombinant HBsAg homogeneity by removing associated aggregates

Production of recombinant HBsAg as a main component of the hepatitis B vaccine has already been established in commercial scale. So far, many studies have been performed to optimize the production process of this recombinant vaccine. However, still aggregation and dissociation of rHBsAg virus-like particles (VLPs) are major challenges in downstream processing of this biomedicine. The structural diversity of rHBsAg is dependent on many factors including cell types, molecular characteristics of the expressed recombinant rHBsAg, buffer composition as well as operation condition and specific characteristics of each downstream processing unit. Hence, it is not relatively easy to implement a single strategy to prevent aggregation formation in already established rHBsAg production processes. In this study, we examined the efficacy of weak anion exchange chromatography (IEC)- packed with DEAE Sepharose Fast Flow medium- on isolation of rHBsAg VLPs from aggregated structures. For this purpose, the influence of ionic strength of elution buffer as a key factor was investigated in isolation and recovery of rHBsAg VLPs. The elution buffer with electrical conductivity between 27 and 31 mS/cm showed the best results for removing aggregated rHBsAg based on SEC-HPLC analysis. The results showed that in the selected conductivity range, about 79% of rHBsAg was recovered with purity above 95%. The percentage of rHBsAg VLPs in the recovered sample was between 94% and 97.5% indicating that we could obtain highly homogeneous rHBsAg within the acceptable quality level. The TEM, SDS-PAGE and western blot analysis were also in agreement with our quantitative measurements.

Enhanced cell disruption strategy in the release of recombinant hepatitis B surface antigen from Pichia pastoris using response surface methodology

BACKGROUND

Cell disruption strategies by high pressure homogenizer for the release of recombinant Hepatitis B surface antigen (HBsAg) from Pichia pastoris expression cells were optimized using response surface methodology (RSM) based on the central composite design (CCD). The factors studied include number of passes, biomass concentration and pulse pressure. Polynomial models were used to correlate the above mentioned factors to project the cell disruption capability and specific protein release of HBsAg from P. pastoris cells.

RESULTS

The proposed cell disruption strategy consisted of a number of passes set at 20 times, biomass concentration of 7.70 g/L of dry cell weight (DCW) and pulse pressure at 1,029 bar. The optimized cell disruption strategy was shown to increase cell disruption efficiency by 2-fold and 4-fold for specific protein release of HBsAg when compared to glass bead method yielding 75.68% cell disruption rate (CDR) and HBsAg concentration of 29.20 mg/L respectively.

CONCLUSIONS

The model equation generated from RSM on cell disruption of P. pastoris was found adequate to determine the significant factors and its interactions among the process variables and the optimum conditions in releasing HBsAg when validated against a glass bead cell disruption method. The findings from the study can open up a promising strategy for better recovery of HBsAg recombinant protein during downstream processing.