Recent trends of heavy metal removal from water/wastewater by membrane technologies

Summary
By the time the complete genome sequence of the soil bacterium Pseudomonas putida KT2440 was published in 2002 (Nelson et al., 2002) this bacterium was considered a potential agent for environmental bioremediation of industrial waste and a good colonizer of the rhizosphere. However, neither the annotation tools available at that time nor the scarcely available omics data—let alone metabolic modeling and other nowadays common systems biology approaches—allowed them to anticipate the astonishing capacities that are encoded in the genetic complement of this unique microorganism. In this work we have adopted a suite of state-of-the-art genomic analysis tools to revisit the functional and metabolic information encoded in the chromosomal sequence of strain KT2440. We identified 242 new protein-coding genes and re-annotated the functions of 1548 genes, which are linked to almost 4900 PubMed references. Catabolic pathways for 92 compounds (carbon, nitrogen and phosphorus sources) that could not be accommodated by the previously constructed metabolic models were also predicted. The resulting examination not only accounts for some of the known stress tolerance traits known in P. putida but also recognizes the capacity of this bacterium to perform difficult redox reactions, thereby multiplying its value as a platform microorganism for industrial biotechnology.

The revisited genome of Pseudomonas putida KT2440 enlightens its value as a robust metabolic chassis.

The Vroman effect: competitive protein exchange with dynamic multilayer protein aggregates.

Comparative assessment of downstream processing options for lactic acid

Enzymatic mechanism and biochemistry for cyanide degradation: a review.

Summary
The current knowledge of trehalose biosynthesis under stress conditions is incomplete and needs further research. Since trehalose finds industrial and pharmaceutical applications, enhanced accumulation of trehalose in bacteria seems advantageous for commercial production. Moreover, physiological role of trehalose is a key to generate stress resistant bacteria by metabolic engineering. Although trehalose biosynthesis requires few metabolites and enzyme reactions, it appears to have a more complex metabolic regulation. Trehalose biosynthesis in bacteria is known through three pathways – OtsAB, TreYZ and TreS. The interconnections of in vivo synthesis of trehalose, glycogen or maltose were most interesting to investigate in recent years. Further, enzymes at different nodes (glucose-6-P, glucose-1-P and NDP-glucose) of metabolic pathways influence enhancement of trehalose accumulation. Most of the study of trehalose biosynthesis was explored in medically significant Mycobacterium, research model Escherichia coli, industrially applicable Corynebacterium and food and probiotic interest Propionibacterium freudenreichii. Therefore, the present review dealt with the trehalose metabolism in these bacteria. In addition, an effort was made to recognize how enzymes at different nodes of metabolic pathway can influence trehalose accumulation.

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Trends in bacterial trehalose metabolism and significant nodes of metabolic pathway in the direction of trehalose accumulation

Lactic acid extraction was studied with two extractants, trioctyl amine (TOA) and Aliquat 336, in three diluents (methylisobutyl ketone (MIBK), octanol and paraffin liquid). The effects of organic phase extractant concentration and aqueous phase pH on the extraction process were examined. Among the extractants, TOA was found to be a better extractant than Aliquat 336 in all the diluents. In experiments with 50% (v/v) TOA in methylisobutyl ketone, 79% lactic acid could be extracted (initial lactic acid concentration 86·96 g dm−3). MIBK had a profound effect on the extraction behaviour of TOA in comparison with octanol and paraffin liquid while none of the diluents affected the extraction with Aliquat 336. The extraction of lactic acid was favoured at low pH. The toxicities of TOA and the diluents to Lactobacillus rhamnosus NRRL B445 were also studied. While TOA was found to be highly toxic at the molecular and the phase level, the paraffin liquid was totally non-toxic. The extraction of glucose and yeast extract by TOA and the diluents used was found to be low, which thus enables the selective extraction of lactic acid. © 1998 SCI

Study of lactic acid extraction with higher molecular weight aliphatic amines

The biotransformation of acrylonitrile was investigated using thermophilic nitrilase produced from a new isolate Streptomyces sp. MTCC 7546 in both the free and immobilized state. Under optimal conditions, the enzyme converts nitriles to acids without the formation of amides. The whole cells of the isolate were immobilized in agar-agar and the beads so formed were evaluated for 25 cycles at 50°C. The enzyme showed a little loss of activity during reuse. Seventy-one per cent of 0.5 M acrylonitrile was converted to acid at 6 h of incubation at a very low density of immobilized cells, while 100% conversion was observed at 3 h by free cells.

Nitrilase-catalysed conversion of acrylonitrile by free and immobilized cells of Streptomyces sp.

Suitability of crude glycerol obtained from biodiesel waste for the production of trehalose and propionic acid

Use of an osmotically sensitive mutant of Propionibacterium freudenreichii subspp. shermanii for the simultaneous productions of organic acids and trehalose from biodiesel waste based crude glycerol.

Bijan Choudhury

Papers

Trends in bacterial trehalose metabolism and significant nodes of metabolic pathway in the direction of trehalose accumulation

Study of lactic acid extraction with higher molecular weight aliphatic amines

Nitrilase-catalysed conversion of acrylonitrile by free and immobilized cells of Streptomyces sp.

Suitability of crude glycerol obtained from biodiesel waste for the production of trehalose and propionic acid

Use of an osmotically sensitive mutant of Propionibacterium freudenreichii subspp. shermanii for the simultaneous productions of organic acids and trehalose from biodiesel waste based crude glycerol.