Katarzyna Czaczyk

Why do microorganisms produce rhamnolipids

We review the environmental role of rhamnolipids in terms of microbial life and activity. A large number of previous research supports the idea that these glycolipids mediate the uptake of hydrophobic substrates by bacterial cells. This feature might be of highest priority for bioremediation of spilled hydrocarbons. However, current evidence confirms that rhamnolipids primarily play a role in surface-associated modes of bacterial motility and are involved in biofilm development. This might be an explanation why no direct pattern of hydrocarbon degradation was often observed after rhamnolipids supplementation. This review gives insight into the current state of knowledge on how rhamnolipids operate in the microbial world.

Bacterial biofilms on food contact surfaces - a review.

Bacterial Biofilms on Food Contact Surfaces - a Review This review will discuss some of the basic concepts concerning biofilm formation, development and control in the food industry. Biofilm formation process on food contact surfaces can have a detrimental effect on the microbial status of food. The presence of biofilm on abiotic materials can contaminate the product through direct contact. As a consequence, food spoilage is likely to occur that may lead to reduced shelf life and increased risk of food poisoning from pathogens. Bacteria colonizing food processing surfaces are extremely difficult to eradicate. Biofilms can tolerate antimicrobial agents at concentrations of 10-1000 times that needed to inactivate genetically equivalent planktonic bacteria. A better understanding of bacterial adhesion process is needed for the production of microbiologically-safe and good-quality products in the food industry.

Kraft lignin/silica-AgNPs as a functional material with antibacterial activity.

Advanced functional silica/lignin hybrid materials, modified with nanosilver, were obtained. The commercial silica Syloid 244 was used, modified with N-(2-aminoethyl)-3-aminopropyltrimethoxysilane to increase its chemical affinity to lignin. Similarly, kraft lignin was oxidized using a solution of sodium periodate to activate appropriate functional groups on its surface. Silver nanoparticles were grafted onto the resulting silica/lignin hybrids. The systems obtained were comprehensively tested using available techniques and methods, including transmission electron microscopy, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, elemental analysis and atomic absorption spectroscopy. An evaluation was also made of the electrokinetic stability of the systems with and without silver nanoparticles. Conclusions were drawn concerning the chemical nature of the bonds between the precursors and the effectiveness of the method of binding nanosilver to the hybrid materials. The antimicrobial activity of the studied materials was tested against five species of Gram-positive and Gram-negative bacteria. The addition of silver nanoparticles to the silica/lignin hybrids led to inhibition of the growth of the analyzed bacteria. The best results were obtained against Pseudomonas aeruginosa, a dangerous human pathogen.

Vitamin B12 production from crude glycerol by Propionibacterium freudenreichii ssp. shermanii: Optimization of medium composition through statistical experimental designs

A two-step statistical experimental design was employed to optimize the medium for vitamin B(12) production from crude glycerol by Propionibacterium freudenreichii ssp. shermanii. In the first step, using Plackett-Burman design, five of 13 tested medium components (calcium pantothenate, NaH(2)PO(4)·2H(2)O, casein hydrolysate, glycerol and FeSO(4)·7H(2)O) were identified as factors having significant influence on vitamin production. In the second step, a central composite design was used to optimize levels of medium components selected in the first step. Valid statistical models describing the influence of significant factors on vitamin B(12) production were established for each optimization phase. The optimized medium provided a 93% increase in final vitamin concentration compared to the original medium.

Conversion of glycerol to 1,3-propanediol by Citrobacter freundii and Hafnia alvei - newly isolated strains from the Enterobacteriaceae.

In this study, nearly 4000 bacterial strains from the family of Enterobacteriaceae isolated from different environments were screened for ability to convert glycerol to 1,3-propanediol (1,3-PD). The aim of the research was to isolate 1,3-PD producers from the natural environment, identify and characterize the best isolates. Three selective media were tested to usefulness in the isolation of bacteria from the family Enterobacteriaceae. Only, 28% of examined isolates could synthesize 1,3-PD from glycerol. 1,3-PD producing bacteria were identified by API 20E tests and 16S rRNA sequences to be Klebsiella pneumoniae, Klebsiella oxytoca, Citrobacter freundii and Hafnia alvei. It is the first time, when the fermentation glycerol to 1,3-PD by H. alvei was investigated. The selected strains (C. freundii AD119 and H. alvei AD27) were analyzed on a bioreactor scale under constant pH value 7.0 at temperature of 30°C and 37°C. After 40h in batch fermentation, H. alvei AD27 produced 11.3g/L of 1,3-PD at 37°C. For C. freundii AD119, the best results were obtained at temperature of 30°C. After 24h of fermentation, the 1,3-PD concentration reached above 23 g/L of 1,3-PD.

Biotechnological synthesis of 1,3-propanediol using Clostridium ssp.

1,3-Propanediol (PD) is an important chemical product which can be used for synthesis reactions, in particular, as a monomer for polycondensations to produce polyesters, polyethers and polyurethanes. It is produced by two methods, chemical synthesis and microbial conversion. Recently, the increasing interest in microbial conversion was observed. Glycerol is used as a substrate in this process and it may be fermented to 1,3-PD by, among others, Citrobacter ssp., Klebsiella ssp., Lactobacillus ssp., Enterobacter ssp. and Clostridium ssp. strains. The process of microbiological bioconversion pathway of glycerol to 1,3-PD is well known for a long time but microorganisms taking part in this fermentation are pathogenic. Thus, natural producers of 1,3-PD that are non-pathogenic and efficient enough, are still sought. This review deals with the case of 1,3-PD production and microbial formation of 1,3-PD, especially by Clostridium ssp. Moreover, it presents genetic engineering methods used in increasing microorganisms’ efficiency in the glycerol to 1,3 PD fermentation. Key words : 1,3-Propanediol, Clostridium ssp., fermentation, glycerol.

Isolation process of industrially useful Clostridium bifermentans from natural samples

A selective isolation procedure of clostridial strains from natural samples able to convert glycerol to 1,3-propanediol (1,3-PD) and organic acids was investigated. The modified PY medium of high concentration of NaHCO(3) was shown to be highly selective for Clostridium bifermentans. Obtained isolates produced mainly 1,3-PD, lactic, acetic, and formic acids from glycerol.

Improved Utilization of Crude Glycerol By-Product from Biodiesel Production

During the last ten years a significant increase in biodiesel production and its commercial applications was observed (Rahmat et al., 2010). Nowadays, biodiesel is only one alternative fuel which may replace crude oil because it can be use in vehicles with a diesel engine without modifications of major engine or fuel elements (Johnson & Taconi, 2007). Presently, the most often used biodiesel fuels are vegetable oil fatty acid methyl or ethyl esters produced by transesterification (Andre et al., 2010; Sendzikiene et al., 2007). For every three mol of ethyl esters one mol of crude glycerol is produced, which is equivalent to approximately 10 wt% of the total biodiesel production (Karinen & Krause, 2006; Pagliaro at al., 2009; Rahmat et. al., 2010). It is estimated that by 2016 the world biodiesel market will achieve the quantity of 37 billion gallons, which means that significantly more than 4 billion gallons of crude glycerol will be produced every year. The potential sale of this fraction might have an influence on the total price of biodiesel and make it cheaper (Fan et al., 2010; L. Wang et al., 2006). Pure glycerol may be used in many branches of industry, for example in food products (to sucrage liqueurs), cosmetics (as a moisturizing factor), textile industry, in pharmaceuticals, cellulosic industries; moreover, one can use it in nitrocellulose production as well as a supplement in fodder for pigs, swine, and hogs (Pagliaro et al., 2007; Z.X. Wang et. al., 2001). In contrast, use of raw glycerol is strictly limited because of its composition and a presence of pollutant substances. The main pollutants of this raw material include spent catalysts, residual methanol, mineral salts, heavy metals, monoand diacylglycerols, free fatty acids and soaps (Dasari, 2007). The main biodiesel producers, thanks to the adequate installations inside their production plants, are able to purify raw glycerol. This is done via filtration, chemical steps, and filtration vacuum distillation. Then the technical grade glycerol (>97% pure, used for industrial type applications) or even refined USP grade glycerol (>99.7% pure, used in cosmetics, pharmaceuticals or food) is obtained. Unfortunately, such installations are too expensive for small or medium production plants. One solution to this problem is to sell raw glycerol to refineries in order to increase its value. Nevertheless, glycerol producers must pay for transportation of this glycerol fraction. Because transportation cost often equals or exceeds the price of raw glycerol, it does not make sense. Accordingly, this solution cannot be accepted (Johnson & Taconi, 2007). Therefore, new uses for crude glycerol must be sought and, luckily, many innovative methods of utilizations of this waste are under investigation. This chapter

Investigation of the effectiveness of disinfectants against planktonic and biofilm forms of P. aeruginosa and E. faecalis cells using a compilation of cultivation, microscopic and flow cytometric techniques

This study evaluated the effectiveness of selected disinfectants against bacterial cells within a biofilm using flow cytometry, the conventional total viable count test and scanning electron microscopy (SEM). A flow cytometric procedure based on measurement of the cellular redox potential (CRP) was demonstrated to have potential for the rapid evaluation of activity against biofilm and planktonic forms of microbes. Quaternary ammonium compound-based disinfectant (QACB) demonstrated a higher level of anti-microbial activity than a performic acid preparation (PAP), with mean CRP values against P. aeruginosa cells of 2 and 1.33 relative fluorescence units (RFU) vs 63.33 and 61.33 RFU for 8 and 24 h cultures respectively. Flow cytometric evaluation of the anti-biofilm activity demonstrated a higher efficacy of QACB compared to PAP for P. aeruginosa cells of 1 and 0.66 RFU vs 18.33 and 22.66 RFU for 8 and 24 h cultures respectively. SEM images of treated P. aeruginosa cells demonstrated disinfectant-specific effects on cell morphology.

Influence of phenolic acids on indole acetic acid production and on the type III secretion system gene transcription in food-associated Pseudomonas fluorescens KM05

The purpose of these investigations was to evaluate the reduction capability of phenolic acids (ferulic, chlorogenic, gallic, and p-coumaric acids) on indole acetic acid synthesis by food-associated Pseudomonas fluorescens KM05. Specific genetic primer for the type III secretion system (TTSS) in P. fluorescens KM05 was designed and the influence of phenolic acids on its expression was investigated. In the work the ferulic and chlorogenic acids at the concentration of 0.02 and 0.04 μg/ml affected on bacterial growth pattern and the signal molecules production. The phenolic acids, that were appreciable effective against P. fluorescens KM05 indole acetic acid production, significantly suppressed TTSS gene.