The effect of pH regulation on biohydrogen production was studied using suspended and immobilized mixed cultures. Four sets of experiments were conducted using suspended cells under regulated pH (Sus_R) and non-regulated pH conditions (Sus_N) as well as alginate-immobilized cells under pH regulated (Imm_R) and non-pH regulated conditions (Imm_N). Sus_R showed a peak hydrogen fraction of 44% and complete glucose degradation, compared to Sus_N with a peak hydrogen fraction of 36% and a glucose degradation of 37%. Imm_R experiments showed a peak biohydrogen fraction of 35%, while the peak hydrogen fraction observed with Imm_N was 22%. The highest hydrogen fraction was observed using suspended cells under regulated pH conditions. A 100% glucose degradation was observed in both pH regulated and non-regulated processes using immobilized cells. The rate of pH change was slower for immobilized cells compared to suspended cells suggesting a better buffering capacity under non pH regulated conditions. The study showed that biohydrogen production with suspended cells in a non-regulated pH environment resulted in early termination of the process and lower productivity.

We describe a competitive colorimetric assay that enables rapid and sensitive detection of galactose and reduced nicotinamide adenine dinucleotide (NADH) via colorimetric readouts and demon-strates its usefulness for monitoring NAD+-driven enzymatic reactions. We present a sensitive plasmonic sensing approach for assessing galactose concentration and the presence of NADH using galactose dehydrogenase immobilized gold nanostars (AuNS-PVP-GalDH). The AuNS-PVP-GalDH assay remains turquoise blue in the absence of galactose and NADH; however, as galactose and NADH concentrations grow, the reaction well color changes to a characteristic red color in the presence of an alkaline environment and metal ions catalyst (detection solution). As a result, when galactose is sensed in the presence of H2O2, the colored response of the AuNS-PVP-GalDH assay transforms from turquoise blue to light pink, then to wine red in a con-centration-dependent manner discernible to the human eye. This competitive AuNS-PVP-GalDH assay could be a viable analytical tool for rapid and convenient galactose quantification in re-source-limited areas.

Currently, the textile industry is among the most rapidly expanding areas of the economy and is an important source of water pollution. There are many efficient chemical and physical methods for treating textile effluent, but they produce secondary pollutants. Therefore, there is a need to manage the textile waste wastewater. The potential EPS-producing and plant growth-promoting rhizobacteria Lysinibacillus capsici PB300 (T) bacteria strain has been isolated from the bark borer-affected Peltophorum pterocarpum plant and has been determined to be effective in > 95 decolorizing Reactive Red 120, and other azo dyes such as AB11385%, orange II 94.62%, Congo red 94.62%, phenol red 94.54%, and mixtures of azo dyes 81.66%. Physico-chemical factors were optimized manually, including Taguchi design. EPS production, PGPR strain, and fabric discoloration of L. capsici were qualitatively studied. The FTIR, GC-MS, and UV absorbance studies also confirmed that the dye had been broken into its amines. Research findings using enzyme assays have shown that the bacteria Lysinibacillus capsici PB300 (T) can utilize laccase and manganese peroxidase and are capable of degrading dyes significantly. According to this work, immobilised L. capsici cells and the studied four bacterial consortiums, Lysinibacillus capsici PB300 (T), Alcaligenes faecalis subsp. Phenolicus DSM 16503 (T), Acinetobacterbaumanni ATCC 19606 (T), and Pseudomonasaeruginosa JCM 5962 may be employed to degrade RR120 effectively, and it is concluded that L. capsici PB300 (T) bacteria is significantly efficient in textile effluent treatment.

Due to the ever increasing global warming, the scientific community is concerned with finding immediate solutions to reduce or utilize carbon dioxide (CO2) and convert it in useful compounds. In this context, the reductive process of CO2 methanation is well investigated and attractive due to its simplicity. However, it requires the development of highly active catalysts. In this mini-review, the focus is on biochar-immobilized nanocatalysts for CO2 methanation. We summarize the recent literature on the topic, reporting strategies for the design of biochar with immobilized nanocatalysts and their performances in CO2 methanation. We review the thermochemical transformation of biomass into biochar and its decoration with CO2 methanation catalysts. We also tackle direct methods of obtaining biochar-nanocatalysts, in one pot, from nanocatalyst precursor-impregnated biomass. We review the effect of the initial biomass nature, as well as the conditions that permit to tune the perfomances of the composite catalysts. Finally, we discuss the CO2 methanation performances and how they could be improved keeping in mind low operation cost and particularly sustainability.

The conjugation of phytosterols (PSs) with fatty acids results in producing phytosterol esters (PSEs) characterized with enhanced lipophilicity and improved functional properties of major interest in food and nutraceutical applications. The use of immobilized lipases to catalyze direct transesterification reactions between PSs and plant oils to form PSEs as a green alternative to conventional chemical production methods has attracted interest during the last two decades. The low solubility of PSs in common plant oil triglycerides, typically below 3% at ambient temperatures, remains the main challenge for bringing lipase-catalyzed direct transesterification reactions of PSs and oil triglycerides to commercial scales. This study focuses on the enzymatic synthesis of PSEs starting from solubilized PSs at concentrations of up to 30% wt./wt. of oil mixtures comprising fatty acid ethyl esters (FAEEs), monoglycerides (MGs), diglycerides (DGs) and triglycerides (TGs) as a homogeneous medium for the direct transesterification reaction. The results of this study show for the first time that the addition of FAEEs into the reaction medium results in altering of the substrate preference of the enzyme making MGs as the favorite fatty acyl group donors for PSs amongst all other fatty acyl donors present in the reaction system. The proposed new enzymatic route allows starting with high concentrations of solubilized PSs making the direct transesterification of oil glycerides attractive for production of PSEs at industrials scales.

Esters are versatile compounds with a wide range of applications in various industries due to their unique properties and pleasant aromas. Conventionally, the manufacture of these compounds has relied on the chemical route. Nevertheless, this technique employs high temperatures and inorganic catalysts, resulting in undesired additional steps to purify the final product by removing solvent residues, which decreases environmental sustainability and energy efficiency. In accordance with the principles of “Green Chemistry” and the search for more environmentally friendly methods, a new alternative, the enzymatic route, has been introduced. This technique uses low temperatures and does not require the use of solvents, resulting in more environmentally friendly final products. In spite of the large number of studies published on the biocatalytic synthesis of esters, little attention has been paid to the reactors used for it. Therefore, it is convenient to gather the scattered information regarding the type of reactor employed in these synthesis reactions, considering the industrial field in which the process is carried out. The comparison between the performance of the different reactor configurations will allow us to draw the appropriate conclusions regarding their suitability for each specific industrial application.

In this paper, Akbari-Ganji's and Taylor series methods are applied to find analytical solutions to nonlinear differential equations that arise in an immobilized-cell photobioreactor. Approximate analytical expressions for substrate and product concentrations and both liquid and gas phases for various parameter values are derived using both methods. Efficiency, accuracy, and convergence of the two methods relative to highly accurate numerical methods are investigated to establish reliable profiles of these two methods for solving general nonlinear equations that model various physical phenomena. Numerical simulations are presented to validate the theoretical investigations.