The study reports the synthesis of fructo-oligosaccharide (FOS) from sucrose using invertase derived from Saccharomyces cerevisiae. The reaction was conducted in a batch mode under free enzyme condition. Fructo-oligosaccharide formation was detected at a high sucrose concentration of over 200 g/L. The investigation was extended to study the effect of different parameters such as initial sucrose concentration (ISC), pH, and enzyme concentration. A maximum FOS yield of 10 % (dry basis) was observed using 525 g/L of ISC, with 6 U/mL of the enzyme, and pH 5.5 at 40 °C. 1-Kestose was the major product of among different forms of FOS. The FOS yield increased with an increase in sucrose concentration up to 525 g/L, beyond which it started to decrease. However, the maximum FOS yield was not affected by the increasing concentration of the enzyme beyond a certain level (2 U/mL). Furthermore, the activity of enzyme slightly increased with an increase in the pH up to 6, and thereafter it declined. Addition of glucose decreased the FOS yield because of enzyme inhibition. A five-step, ten-parameter model was developed, for which the simulation was performed in COPASI. The results predicted by the model were consistent with the experimental data.

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Low band gap photocatalysts are desirable for efficient performance. We report synthesis of cobalt‐doped TiO2 photocatalysts, inside radial pores of nano‐spherical silica (RPNS) particles, having different weight percentages of dopant (0.1 to 4 wt.% Co‐TiO2‐RPNS). Doping decreases both optical band gap and electron‐hole charge separation, with maximum decrease in charge transfer resistance, for 1 wt.% Co‐TiO2‐RPNS (0.74 kΩ.cm−2), compared to TiO2‐RPNS (1.18 kΩ.cm−2). However, it shows only partial degradation of rhodamine B dye. Hence, the 1 wt.% Co‐TiO2‐RPNS catalyst was further investigated with respect to different e−/h+ recombination processes, in presence of any one of the scavengers ‐ e− (K2S2O8) or OH* (butanol) or h+ (EDTA). An e− scavenger shows a higher dye degradation (rate constant 1.24 h−1), while h+ scavenger shows a lower rate (0.38 h−1), in contrast to no scavenger (0.91 h−1). Oxygen purging as a reaction promoter inhibited e−/h+ recombination, doubling overall rate (4.66 h−1). So, scavenger and oxygen purging together can further enhance a low band gap photocatalyst's activity.

Treatment of water-polluting contaminants needs significant improvement to enable the designing of a photocatalytic reactor. This work involves a TiO 2 coated catalyst film in a batch reactor, formed by dip coating on a quartz tube's external surface, highlighting the synthesis and performance of the TiO 2 nanoparticle film. Film optimization was achieved by carrying out one to three coatings on the substrate, using different titanium isopropoxide (TTIP) (TiO 2 precursor) concentrations in isopropanol solvent (volume-by-volume ratio). Photocatalytic degradation of rhodamine B (an indicator dye) was maximum for the sample 5:100 (v/v) (having 460 nm thickness with one dip-coat), giving the highest turnover frequency of 0.342 mol/mol h −1 among all samples. Simultaneously, diffusivity and intrinsic rate constant of the dye through the film were calculated by developing a mathematical model of diffusion and reaction. Such an experimentally validated model can provide insight into the role of composition, film thickness, and other parameters for the most effective degradation of other contaminants too.