A small scale stirred bioreactor was designed and the effect of different agitation rates (30, 60 and 100 rpm) was investigated on HepG2 cells cultured in alginate-chitosan (AC) core-shell microcapsule in terms of the cell proliferation and liver-specific function. The microencapsulated hepatic cells could proliferate well when they were cultured for 10 days at 30 rpm while the cell-laden microcapsules showed no cell proliferation at 100 rpm in the bioreactor system. Albumin production rate, as an important liver function, increased also 1.8- and 1.5- fold under stirring rate of 30 rpm compared to the static culture and 60 rpm of agitation, respectively. Moreover, In comparison with the static culture, about 1.5-fold increment in urea production was observed at 30 rpm. Similarly, the highest expressions of albumin and P450 genes were found at 30 rpm stirring rate, which were 4.9- and 19.2-fold of the static culture. Addition of collagen to the microcapsule core composition (ACol/C) could improve the cell proliferation and functionality at 60 rpm in comparison with the cell-laden microcapsules without collagen. The study demonstrated the hepatic cell-laden ACol/C microcapsule hydrogel cultured in the small scale stirred bioreactor at low mixing rate has a great potential for mass production of the hepatic cells while maintaining liver-specific functions.

The functional properties of food gums are remarkably affected by the quality of solvent/cosolutes and temperature in a food system. In this work, for the first time, the chemical characterizations and dilute solution properties of Lepidium perfoliatum seed gum (LPSG), as an emerging carbohydrate polymer, were investigated. It was found that xylose (14.27%), galacturonic acid (10.70%), arabinose (9.07%) and galactose (8.80%) were the main monosaccharaide components in the LPSG samples. The uronic acid content of LPSG samples was obtained to be 14.83%. The average molecular weight and polydispersity index of LPSG were to be 2.34 × 105 g/mol and 3.3, respectively. As the temperature was increased and the pH was decreased and the concentration of cosolutes (Na+, Ca2+, sucrose and lactose) presented in the LPSG solutions was enhanced, the intrinsic viscosity [η] and coil dimension (Rcoil, Vcoil, υs) of LPSG molecular chains decreased. Activation energy and chain flexibility of LPSG were estimated to be 0.46 × 107 J/kg.mol and 553.08 K, respectively. The relative stiffness parameter (B) of LPSG in the presence of Ca2+ (0.079) was more than that of Na+ (0.032). Incorporation of LPSG into deionized water (0.2%, w/v) diminished the surface activity from 76.75 mN/m to 75.70 mN/m. Zeta potential (ζ) values (−46.85 mV–−19.63 mV) demonstrated that dilute solutions of LPSG had strong anionic nature in the pH range of 3–11. The molecular conformation of LPSG was random coil in all the selected solution conditions. It can be concluded that temperature and presence of cosolutes can significantly influence on the LPSG properties in the dilute systems.

Background In this work, viscoelasticity, flow behaviour, thixotropy and thermo-rheological properties of binary mixtures of Lepidium perfoliatum seed gum (LPSG), as an emerging food gum, and xanthan gum (XG) at various blending ratios of 100:0, 75:25, 50:50, 25:75 and 0:100 were studied for a depth insight into their interaction. FTIR analyses were also done to investigate the interaction between the XG and LPSG. Results FTIR results indicated the hydrogen bond formation between the hydrocolloids. At the linear viscoelastic region (LVE), XG-rich blends exhibited higher tan δLVE and τy, but lower τf. The values of apparent viscosity (ηa) and complex viscosity (η*) diminished with increasing shear rate/frequency, and XG and LPSG individual dispersions showed the greatest and the lowest values, respectively. Based on the extended Cox-Merz rule, a greater shift factor (α) is observed as the ratio of LPSG in the mixed gel increases. At higher fraction of LPSG, except for the fraction of 75%, the thixotropic behaviour appears to be less pronounced. The recovery parameter (R, %) obtained from in-shear structural recovery test decreased with increase in LPSG fraction. The results of non-isothermal kinetic analysis revealed higher thermodynamic incompatibility and immiscibility of LPSG-XG system in the presence of 75% XG. Moreover, according to the results of Cole–Cole plot, the greatest compatibility of LPSG and XG blends was for LPSG75-XG25 sample (β = 0.87), whereas the worst miscibility was found to be for LPSG25-XG75 one (β = 1.02). Conclusions Different rheological properties could be obtained by blending various ratios of LPSG and XG, which in some ratios synergistic behaviour was observed. The wide variety of rheological properties obtained may be appropriate for the use of LPSG-XG mixtures in food industries and pharmaceutical and biomedical applications. Graphical Abstract

To evaluate shear stress influence on ex vivo expansion of hematopoietic cell lineages for clinical application, in this study, human pro-monocytic cell (namely U937 cell line) was selected as a hematopoietic stem cell (HSC) model and cultured in suspension mode at two different agitation rates (50, 100 rpm) in the stirred bioreactor. At the agitation rate of 50 rpm, the cells achieved higher expansion folds (27.4 fold) with minimal morphological changes as well as apoptotic cell death, while at 100 rpm the expansion fold decreased after 5-day of culture in suspension culture in comparison with static culture and reached 24.5 fold at the end of the culture. The results of glucose consumption and lactate production were also in agreement with the data of fold expansion and indicated the preference of culture in the stirred bioreactor when agitated at 50 rpm. This study indicated the stirred bioreactor system with an agitation rate of 50 rpm and surface aeration may be used as a potential dynamic culture system for clinical applications of hematopoietic cell lineage. The current experiments shed data related to the effect of shear stress on human U937 cells, as a hematopoietic cell model, to set a protocol for expansion of HSCs for biomedical applications.

Background In this work, viscoelasticity, flow behaviour, thixotropy and thermo-rheological properties of binary mixtures of Lepidium perfoliatum seed gum (LPSG), as an emerging food gum, and xanthan gum (XG) at various blending ratios of 100:0, 75:25, 50:50, 25:75 and 0:100 was studied for a depth insight into their interaction. FTIR analyses were also done to investigate the interaction between the XG and LPSG. Results FTIR results indicated the hydrogen bond formation between the hydrocolloids At the linear viscoelastic region (LVE), XG-rich blends exhibited higher tan δLVE and τy, but lower τf. The values of apparent viscosity (ηa) and complex viscosity (η*) diminished with increasing shear rate/frequency, and XG and LPSG individual dispersions showed the greatest and the lowest values, respectively. Based on the extended Cox-Merz rule, a greater shift factor (α) is observed as the ratio of LPSG in the mixed gel increases. At higher fraction of LPSG, except for the fraction of 75%, the thixotropic behaviour appears to be less pronounced. The recovery parameter (R, %) obtained from in-shear structural recovery test decreased with increase in LPSG fraction. The results of non-isothermal kinetic analysis revealed higher thermodynamic incompatibility and immiscibility of LPSG-XG system in the presence of higher XG ratio. Moreover, according to the results of Cole-Cole plot, the greatest compatibility of LPSG and XG blends was for LPSG25-XG75 sample (β = 0.87), whereas the worst miscibility was found to be for LPSG75-XG25 one (β = 1.02). Conclusions Different rheological properties could be obtained by blending various ratios of LPSG and XG, which in some ratios synergistic behaviour was observed. The wide variety of rheological properties obtained may be appropriate for the use of LPSG-XG mixtures in food industries, pharmaceutical and biomedical applications.