Ultrasensitive Nanosensor for Detection of Malic Acid in Tomato as Fruit Ripening Indicator

Malic acid is an important fruit ripening indicator. Fruit industry losses every year due to non-availability of rapid technology for early detection of ripening of fruits. Therefore, nanosensor was developed for detection of malic acid concentrations in tomato at early stage of ripening before transport to the market. The enzyme NADP-malate dehydrogenase (Malic enzyme) was covalently immobilized on to screen printed carboxylated-multiwall carbon nanotubes working electrode using EDC-NHS chemistry. The enzyme electrode was characterized using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The immobilized enzyme/c-MWCNT electrode was used for amperometric determination of different concentrations of malic acid in tomato using differential pulse voltammogram (DPV) at scan rate of 100 mv/s. The limit of detection of malic acid was 0.01 mM. The nanosensor showed low K_m (0.12 mM), less response time (2 min), high sensitivity (0.01 mM) and better storage stability 180 days at 4 °C compared to earlier reported malate biosensor. The nanosensor was also validated at different stages of ripening of tomato using enzymatic method.

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Graphical Abstract Nanosensor for detection of malic acid in tomato

     

Ionic liquid as an effective solvent for cell wall deconstructing through astaxanthin extraction from Haematococcus pluvialis

Haematococcus pluvialis is a proficient source of natural antioxidant astaxanthin. However, the efficient extraction of astaxanthin from this microalga remains a great challenge due to the presence of the tough and non-hydrolysable cell walls. In this study, ionic liquid (IL) pretreatment was used for deconstruction of cell wall method. Imidazolium-based ILs exhibited higher cell disruption capability than pyridinium-based and ammonium-based ILs. After the ILs determination, 1-butyl-3-methylimidazolium chloride ([Bmim] Cl) was the most efficient method for cell wall deconstruction that leads to the highest astaxanthin extractability. More than 80% astaxanthin was extracted from H. pluvialis under mild conditions (pretreatment with 40% IL aqueous solution at 35 °C, followed by methanolic extraction at 50 °C). In addition, [Bmim] Cl showed the excellent recyclability, and negligible loss of astaxanthin during IL pretreatment was observed. The present work demonstrates that the combination of IL pretreatment and organic solvent extraction was an energy efficient and eco-friendly process for the astaxanthin recovery from H. pluvialis.     

Comparison of high pressure and thermal pasteurization on the quality parameters of strawberry products: a review

Food Science and Biotechnology - Strawberry (Fragaria ananassa) is rich in bioactive compounds with high antioxidant activity. High pressure processing (HPP) is an efficient alternative to preserve...     

Successful simulation of solution gas drive in heavy oils using conventional modeling

Detailed investigations into the production behavior of heavy oil reservoirs under foamy solution gas drive have been conducted extensively in the past. Historically, two approaches have been used to explain and model the solution gas drive in heavy oil reservoirs. The first approach is the base of foamy oil models in which solution gas drive is governed by parameters such as compressibility, viscosity, nonequilibrium phenomena, and the supersaturation. In the second approach, conventional modeling, which we show to be suitable for the history matching and prediction of the production data and macroscopic modeling of a series of depletion experiments (using a live combination of heavy oil and methane gas in a three-dimensional rectangular laboratory model), the foamy oil flow mechanism, dispersed flow of gas and the supersaturation are nonexistent. The conventional modeling uses parameters such as critical gas saturation, very low gas relative permeability, and the assumption of no supersaturation in the reservoir.     

Bio-hydrogen production from acid hydrolyzed waste ground wheat by dark fermentation

Waste ground wheat was subjected to acid hydrolysis (pH = 3.0) at 90 °C for 15 min using an autoclave. The sugar solution obtained from acid hydrolysis was subjected to dark fermentation for hydrogen gas production after neutralization. In the first set of experiments, initial total sugar concentration was varied between 3.9 and 27.5 g L⁻¹ at constant biomass (cell) concentration of 1.3 g L⁻¹. Biomass concentration was varied between 0.28 g L⁻¹ and 1.38 g L⁻¹ at initial total sugar concentration of 7.2 ± 0.2 g L⁻¹ in the second set of experiments. The highest hydrogen yield (1.46 mol H₂ mol⁻¹ glucose) and the specific formation rate (83.6 ml H₂ g⁻¹ cell h⁻¹) were obtained with 10 g L⁻¹ initial total sugar concentration. Biomass (cell) concentration affected the specific hydrogen production rate yielding the highest rate (1221 ml H₂ g⁻¹ cell h⁻¹) and the yield at the lowest (0.28 g L⁻¹) initial biomass concentration. The most suitable X_o/S_o ratio, maximizing the yield and specific rate of hydrogen gas formation was X_o/S_o = 0.037. Dark fermentation of acid hydrolyzed ground wheat was found to be more beneficial as compared to simultaneous bacterial hydrolysis and fermentation.     

Photo-fermentative hydrogen gas production from dark fermentation effluent of acid hydrolyzed wheat starch with periodic feeding

Hydrogen gas production by photo-fermentation of dark fermentation effluent of acid hydrolyzed wheat starch was investigated at different hydraulic residence times (HRT = 1-10 days). Pure Rhodobacter sphaeroides (NRRL B-1727) culture was used in continuous photo-fermentation by periodic feeding and effluent removal. The highest daily hydrogen gas production (85 ml d⁻¹) was obtained at HRT = 4 days (96 h) while the highest hydrogen yield (1200 ml H₂ g⁻¹ TVFA) was realized at HRT = 196 h. Specific and volumetric hydrogen formation rates were also the highest at HRT = 96 h. Steady-state biomass concentrations and biomass yields increased with increasing HRT. TVFA loading rates of 0.32 g L⁻¹ d⁻¹ and 0.51 g L⁻¹ d⁻¹ resulted in the highest hydrogen yield and formation rate, respectively. Hydrogen gas yield obtained in this study compares favorably with the relevant literature reports probably due to operation by periodic feeding and effluent removal.