B. Jha

Algal lipids, fatty acids and sterols

Abstract: Algae are photosynthetic organisms with ubiquitous distribution and contain varied forms of lipids owing to their extreme habitat diversity. This chapter presents detailed information on the structure and distribution of lipids, fatty acids and sterols in algae together with the genes and enzymes involved in their metabolism. The developments in acclimatory roles of lipids, fatty acids and sterols in response to changes in environmental factors such as nutrients, light, temperature and salinity have been discussed. Further, the current status of lipidomics in algae has also been discussed presuming its promising implications in elucidation of novel lipids and understanding of complex metabolic pathways.

Purification and characterization of κ-carrageenase from a novel γ-proteobacterium,Pseudomonas elongata (MTCC 5261) syn.Microbulbifer elongatus comb. Nov.

The phenotypic and carrageenolytic features of a novel halo tolerant marine bacterium, isolated from decayed red algal samples collected along the west coast of India were studied. This gram-negative strain was identified asPseudomonas elongala (MTCC 5261) syn.Microbulbifer elongalus comb. nov according to its morphological, physiological and molecular characterization. The extracellular κ-carrageenase was purified 106.54-fold by a combination of ammonium sulfate precipitation (40∼60%) and successive gel filtration chromatography. The purified protein fraction yielded significantly high activity of 426.19 units/mg protein and migrated as a single band on a sodium dodecyl sulfate polyacrylamide gel electrophoresis with a molecular weight of ∼128 kDa. For κ-carrageenase activity, optimum temperature was 40°C whereas two pH optimai.e. 5.6 and 7.7 were observed. For κ-carrageenan, the enzyme gave aKm value of 6.66 mg/mL and aVmax value of 4 μmol/min/mg when the reaction was carried out at 40°C and pH 5.6. Isolated κ-carrageenase could successfully generate protoplasts ofKappaphycus alvarezii. This is the first report on the production of κ-carrageenase by this bacterium isolated from west coast of India. Molecular mass and various characteristics showed that the carrageenase fromP. elongata was much different from those previously reported.

Kinetics, Isotherms, and Thermodynamics of Hg(II) Biosorption onto Carica papaya

ABSTRACT Carica papaya, a novel sorbent, was evaluated for sorption of Hg(II) from synthetic aqueous solutions using various pseudo-second order kinetic models as well as equilibrium sorption models. Batch kinetic and equilibrium experiments were carried out for the sorption of Hg(II) onto C. papaya at pH 6.5 and solid to liquid ratio (s/l) 1.0 g L−1. The kinetic data were fitted to second order models of Sobkowsk and Czerwinski, Ritchie, Blanchard, Ho and McKay, whereas Langmuir, Freundlich, and Redlich-Peterson models were used for the equilibrium data. A comparative study on both linear and nonlinear regression showed that the Sobkowsk and Czerwinski and Ritchies second order model were the same. Ho and McKays pseudo-second order model fitted well to the experimental data when compared with the other second order kinetic expressions. Langmuir isotherm parameters obtained from the four Langmuir linear equations by using linear method were dissimilar, but were the same when nonlinear method was used. Additionally, various thermodynamic parameters, such as ΔG 0, ΔH 0, and ΔS 0, were calculated. The negative values of Gibbs free energy (ΔG 0) and ΔH 0 confirmed the intrinsic nature of biosorption process and exothermic, respectively. The negative value of ΔS 0 showed the decreased randomness at the solid-solution interface during biosorption.