Mutagenesis enhances gellan gum production by a novel Sphingomonas spp.: upstream optimization, kinetic modeling, and structural and physico-functional evaluation.

Gellan gum (GG) has gained tremendous attention owing to its diversified applications. However, its high production and hence market cost are still a bottleneck in its widespread utilization. In the present study, high GG producing mutant of Sphingomonas spp. was developed by random mutagenesis using ethyl methylsulphonate (EMS) for industrial fermentation and identified as Sphingomonas trueperi after 16S rRNA and matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS) analysis. The fermentation conditions such as pH, temperature, and inoculum ratio were optimized by one factor at a time (OFAT) followed by screening of medium components by the Plackett-Burman statistical design. The most critical nutrients were further optimized by response surface methodology for maximizing GG production. The effect of dissolved oxygen tension in bioreactor on cell growth, substrate consumption, GG production, and batch productivity was elucidated. The highest GG titer (23 ± 2.4 g/L) was attained in optimized medium at 10% inoculum (6.45 ± 0.5 log cfu/mL) under controlled fermentation conditions of pH (7), temperature (30 °C), agitation (300-600 rpm), and aeration (0.5-2.0 SLPM) at 22 ± 2% dissolved oxygen tension in a 10-L bioreactor. Kinetic modeling of optimized batch process revealed that logistic growth model could best explain biomass accumulation, while GG formation and substrate consumption were best explained by Luedeking-Piret and exponential decay model, respectively. Structural and physico-functional features of GG produced by mutant Sphingomonas spp. were characterized by HPLC, FTIR, NMR, DSC, TGA, GPC, SEM, and rheological analysis. The higher productivity (0.51 g/L/h) under optimized fermentation conditions suggests potential consideration of mutant and process for commercial utilization.

Development of highly reusable, mechanically stable corn starch-based aerogel using glycerol for potential application in the storage of fresh spinach leaves.

Impact of glycerol on the physico-functional, morphological, mechanical, and rehydration properties of corn starch-based aerogel has been investigated. The aerogel was prepared from hydrogel (sol-gel method) using solvent exchange and supercritical CO2 drying. Glycerol-infused aerogel had a more connected, denser structure (0.38-0.45 g/cm3), enhanced hygroscopic behavior, and was reusable up to eight times in terms of its capacity to absorb water after being drawn from the soaked sample. However, the inclusion of glycerol reduced the aerogel's porosity (75.89-69.91 %) and water absorption rate (WAR; 118.53-84.64 %) but enhanced its percentage shrinkage (75.03-77.99 %) and compressive strength (26.01-295.06 N). The most effective models for describing the rehydration behavior of aerogel were determined to be the Page, Weibull, and Modified Peleg models. Glycerol addition improved the internal strength of the aerogel so could be recycled without significant change in the physical characteristics of the aerogel. By effectively eliminating the condensed moisture that was developed inside the packing owing to the transpiration of fresh spinach leaves, the aerogel extended the storage life of the leaves by up to eight days. The glycerol-based aerogel has the potential to be employed as a carrier matrix for various chemicals and a moisture scavenger.

Application of chemometric techniques: An innovative approach to discriminate two seaweed cultivars by physico-functional properties.

Chemometric techniques were employed to discriminate two Indonesian seaweed cultivars (Kappaphycus alvarezii and Sargassum duplicatum) based on their physico-functional properties. Data of physico-functional properties, including emulsifying activity and bulk density, were processed using multivariate, discriminant analysis (DA), principal component analysis (PCA), and cluster analysis (CA). Significant differences (p < 0.05) and discrimination (multivariate analysis (F9,14 = 57.85; Wilks's lambda = 0.02, p < 0.0001)) were determined among physico-functional properties of seaweed powders. In addition, DA method clarified (Λ = 0.02 and χ2 = 63.74) variations between samples along with two discriminate functions. Moreover, PCA (49.63% with Eigenvalues > 1) and CA (clusters 1 and 2) methods confirmed that the seaweed samples possessed differing physico-functional properties, which implied their distinctive use in food product development. Overall, our results demonstrated strong variation in seaweed powers using chemometrics, which might contribute to the rapid applicability of chemometrics in evaluating novel food material.

Physico-functional and antioxidant properties of sand-roasted chickpea (Cicer arietinum).

The effect of roasting on the physical, color, thermal, functional and antioxidant properties of chickpea was investigated. Chickpea grains were roasted in sand at three temperatures (180, 200 and 220°C) for different times (5, 10 and 15min). Highest surface area and lowest bulk density were obtained for grains roasted at 220°C for 15min. The lightness 'L' of flour decreased from 88.48 (unroasted) to 78.73 (220°C, 15min) while significant increase in 'a' and 'b' color values was observed from -0.73 to 2.25 and 22.43 to 24.83, respectively on roasting. Significant decrease in enthalpy of gelatinization (-0.14 to -0.46J/g), enthalpy of amylase-lipid complex (4329-2293J/g), total flavonoid content (22.89-16.64mg quercetin equivalents/100g) and antioxidant activity (22.85-7.36%) was observed upon roasting. However, roasting led to an increase in water absorption capacity (0.89-3.64g/g), water absorption index (1.97-3.52) and oil absorption capacity (1.60-3.54g/g).