No abstract

Bacterial polyesters have shown potential as biodegradable plastics. Microorganisms capable of producing these polyesters from cheaper carbon sources and methods for their ef®cient recovery are widely studied worldwide. Methylobacterium sp V49, an environmental isolate, was cultivated on a mineral salts medium containing different carbon sources. Maximum accumulation of poly-3-hydroxybutyrate (PHB) within the bacterial cell was observed with glucose as the carbon source. Methanol and sugars such as sucrose and lactose also induced PHB accumulation. The effect of C:N ratio on polymer accumulation was studied. Different strategies for the extraction and recovery of the polymer from the cells were compared. A non-solvent-based method using a high-pressure homogenizer in the presence of SDS was found to be the most satisfactory. Maximum recovery of 98% was achieved by homogenizing the cells at 400 kgcm À2 in 5% SDS solution.

Fresh coconut oil was heated under different conditions for 48 hr at 180 C. The heat treatments included heating in vacuo, heating in air and heating in air and water. The samples were distilled under high vacuum and the volatiles thus obtained were analyzed by combined gas chromatography‐mass spectrometry. In all heated samples, a series of n‐alkanes and I‐alkenes, n‐alkanals, methyl alkanones, alkenals, gamma‐and delta‐lactones, methyl and ethyl esters and free fatty acids were identified. The relative amounts of these compounds varied with the type of heat treatment to which the coconut oil was subjected.

Escherichia coli cells with penicillin acylase activity were permeabilized with aqueous solutions of the cationic detergent N-cetyl-N,N,N-trimethylammonium bromide (CTAB), at pH 8.0 and the activity was found to have almost doubled. The concentration of CTAB, the time and temperature of treatment were optimised for maximum enzyme activity and were found to be 0.2%, 20 min and 5'C respectively. Subsequently, the cell bound activity was retained for a longer period by chemical cross-linking with 0.1% glutaraldehyde. INTRODUCTION:

The study was undertaken to develop a suitable design to accommodate liquefying hygroscopic samples in the Proximity Equilibrium Cell (PEC) for equilibration to desired water activity. The system suggested has overcome the limitation of the earlier reported methods using PEC and is found to be rapid compared to other gravimetric methods used for hygroscopic materials.