Isolation and characterization of the extracellular lipase of Acinetobacter calcoaceticus 69 V

Effects of Nonionic Surfactants on Xanthan Gum Production: a Survey on Cellular Interactions

Background

Xanthomonas campestris is a biopolymer producing gram negative bacterium. Production of xanthan biopolymer can be affected by different extrinsic factors as well as surfactants. Hitherto, effects of nonionic surfactants on xanthan production have been studied in a limited number of articles.

Objective

In the present study, nonionic surfactants were used to pursue their effects on improvement of xanthan production. Moreover, a number of cellular consequences upon the treatment were investigated with impacts on gum production.

Materials and Methods

Effects of different nonionic surfactants (Tween 20, Tween 80 and Triton X100) on xanthan production and Xanthomonas campestris cells were assessed by ultramicroscopy (SEM), changes in culture turbidity, leakage of sugars and ATP, and quality of xanthan (i.e. pyruvate content and determination of polymer molecular weight).

Results

The nonionic surfactant Tween 20 increased ATP (3.2 folds) and sugar leakage (3.1 folds). Furthermore, they caused cell shape alteration. Tween 80 improved both xanthan production (11 g.L^-1) and viscosity of the product (1368 cP), while the total biomass remained unchanged (2.2 g.L^-1). Molecular weight of xanthan was enhanced (from 23 to 59 million Da). Toxic effect of 5% (v/v) Triton X 100 decreased the turbidity of culture to 120 NTU and total biomass was diminished to 1 g.L^-1. Tween 20 caused the loss of ATP and sugar leakage and led to lower xanthan production. It had no effect on biomass content.

Conclusions

In general, amounts of surfactants that bacterial cells can tolerate seem to be helpful in substrate and metabolite transportation, and enzyme activities involved in xanthan biosynthesis and release. Surfactants induce harsh damages to cell barriers, preventing the growth and adversely affecting quantity and quality of xanthan gum.

Effects of warming on stream biofilm organic matter use capabilities

The understanding of ecosystem responses to changing environmental conditions is becoming increasingly relevant in the context of global warming. Microbial biofilm communities in streams play a key role in organic matter cycling which might be modulated by shifts in flowing water temperature. In this study, we performed an experiment at the Candal stream (Portugal) longitudinally divided into two reaches: a control half and an experimental half where water temperature was 3 °C above that of the basal stream water. Biofilm colonization was monitored during 42 days in the two stream halves. Changes in biofilm function (extracellular enzyme activities and carbon substrate utilization profiles) as well as chlorophyll a and prokaryote densities were analyzed. The biofilm in the experimental half showed a higher capacity to decompose cellulose, hemicellulose, lignin, and peptidic compounds. Total leucine-aminopeptidase, cellobiohydrolase and β-xylosidase showed a respective 93, 66, and 61% increase in activity over the control; much higher than would be predicted by only the direct temperature physical effect. In contrast, phosphatase and lipase activity showed the lowest sensitivity to temperature. The biofilms from the experimental half also showed a distinct functional fingerprint and higher carbon usage diversity and richness, especially due to a wider use of polymers and carbohydrates. The changes in the biofilm functional capabilities might be indirectly affected by the higher prokaryote and chlorophyll density measured in the biofilm of the experimental half. The present study provides evidence that a realistic stream temperature increase by 3 °C changes the biofilm metabolism to a greater decomposition of polymeric complex compounds and peptides but lower decomposition of lipids. This might affect stream organic matter cycling and the transfer of carbon to higher trophic levels.

Optimization of culture conditions for production of a novel cold-active lipase from Pichia lynferdii NRRL Y-7723

Lipases with abnormal properties such as thermostability, alkalinity, acidity, and cold activity receive industrial attention because of their usability under restricted reaction conditions. Most microbial cold-active lipases originate from psychrotrophic and psychrophilic microorganisms found in Antarctic regions, which has led to difficulties in the practical production of cold-active lipase. Recently, a mesophilic yeast, Pichia lynferdii NRRL Y-7723, was reported to produce a novel cold-active lipase. This study focused on optimization of environmental factors, while giving particular attention to the relationships between given factors and incubation time, to maximize the production of a novel cold-active lipase from P. lynferdii NRRL Y-7723. Maximum lipase production was highly dependent on the incubation time at a given environmental factor. Lipase production varied with incubation time at a given temperature, and 20 °C was selected as the optimum temperature for lipase production. Fructose was selected as the best carbon source, and maximum lipase production was obtained when it was present at 0.7% (w/v). Yeast extract was an efficient organic nitrogen source, with maximum lipase production occurring at 0.9% (w/v). Specifically, at the optimum yeast extract level the lipase production was >10 times higher than the productivity under standard conditions. All natural oils tested showed lipase production, but their maximum productivities varied according to incubation time and oil species.

Acinetobacter lipases: molecular biology, biochemical properties and biotechnological potential

Lipases (EC 3.1.1.3) have received increased attention recently, evidenced by the increasing amount of information about lipases in the current literature. The renewed interest in this enzyme class is due primarily to investigations of their role in pathogenesis and their increasing use in biotechnological applications. Also, many microbial lipases are available as commercial products, the majority of which are used in detergents, cosmetic production, food flavoring, and organic synthesis. Lipases are valued biocatalysts because they act under mild conditions, are highly stable in organic solvents, show broad substrate specificity, and usually show high regio- and/or stereo-selectivity in catalysis. A number of lipolytic strains of Acinetobacter have been isolated from a variety of sources and their lipases possess many biochemical properties similar to those that have been developed for biotechnological applications. This review discusses the biology of lipase expression in Acinetobacter, with emphasis on those aspects relevant to potential biotechnology applications.