Robert W Lovitt | University of Wales (original) (raw)

Conference Presentations by Robert W Lovitt

Lactobacilli belong to the group of Lactic Acid Bacteria (LAB), extensively utilised in the conte... more Lactobacilli belong to the group of Lactic Acid Bacteria (LAB), extensively utilised in the contemporary food industry. These bacteria are mainly used as natural acidifiers, for the inoculation of bulk quantities of milk and vegetables, in order to produce a variety of fermented products. As such, large quantities of their biomass, produced in cost effective enviromentaly friendly nutrient media, are necessary. Furthermore, during their growth, they naturally produce antimicrobial substances, called bacteriocins or lantibiotics. Due to the constantly developing need for natural food preservatives, bacteriocins deriving from Lactobacilli metabolism, function and activity has been extensively investigated. The possibility of producing these substances in mass quantities was investigated through several techniques. Three known bacteriocin producing strains of Lactobacilli, were carefully selected, L.plantarum NCIMB 8014, L.casei NCIMB 11970 and L.lactis NCIMB 8586. They were grown into simple batch cultures without pH control, where their physicochemical needs were determined. Through the determination of the optimum nutritional conditions for their propagation an optimised growth medium occurred. A simple, liquid turbidometric method was developed to test the bacteriocin productivity of these strains, on the developed media. The antimicrobial activity and potency of the bacteriocins produced, were tested against the target strain L.delbruckii subsp.lactis NCIMB 8117. In an effort to facilitate the extraction of bacteriocins from the fermented broths it was decided , to fabricate a nutrient medium , that would contain, low molecular weight nitrogen sources and equally support high production of bacteriocins and large yields of biomass.

In order to achieve that, the optimised medium was then filtrated via ultrafiltration membrane modules of 30 and 4 kDa MWCO , in an effort to simplify the medium and facilitate the extraction of the produced substance. The medium’s efficiency in supporting the growth and the bacteriocin production of the bacilli was tested and comparative studies between filtrated and unfiltrated media were done.The filtered medium, containing low molecular weight nutrient sources, was proven to to successfully support growth and bacteriocin production.

Keywords: LAB, Bacteriocins, Target strain, Ultrafiltration, Growth rate, DT.

Introduction Three Lactobacilli strains, Lactobacillus casei NCIMB 11970 Lactobacillus plantarum... more Introduction
Three Lactobacilli strains, Lactobacillus casei NCIMB 11970 Lactobacillus plantarum NCIMB 8014, Lactobacillus lactis NCIMB 8586 have been used for the production of bacteriocins. Though their production phase, their biochemical nature , their mode of activity even their genetic structure have been widely investigated, there are hardly any studies investigating their potency and activity in depth of time, in other words their self life under several physicochemical conditions that may occur during their production in large scale.
As such the effect of several factors influencing the activity and the potency of bacteriocins when produced in large scale were examined as due to bacteriocins peptide nature be degradation or denaturation might occur, under extreme physicochemical conditions. During scale up process, differences between the output data may occur, such as concerning biomass, metabolic by products and limiting substrate concentrations. These may affect negatively, the activity and the potency of the bacteriocins. For investigating these effects and minimising them, numerous studies were conducted, which were related to the exact phase of the production of these substances, the effect of dilution and temperature changes. These studies could be used in order to minimise the scaling up effect when decided to produce these peptides in large scale.
. Materials and Methods
Nisin solutions of 1000 IU/ml, crude extracts of the fermented media by Lactobacilli and treated supernatants containing bacteriocins were serially diluted. These were tested for potency against the indicator strain L.delbruckii subsp.lactis NCIMB 8117 and their activity was calculated in international units per millilitre (IU/ml) according to the dose response model fabricated. Mechanical stress was applied to the produced bacteriocins and nisin through microfiltration (0.2μm MWCO) and ultrafiltration (30kDa MWCO). Heat tolerance was also tested in a range of temperature of 40, 60, 80 and 100°C for 15, 30, 45, and 60 minutes time interval in each temperature. The stability of the bacteriocins in low temperatures was also tested. The solutions were kept in 4°C for 12, 48, 60, 72, 84 and 96h.

Results
The bacteriostatic effect of the produced bacteriocins and nisin treated with several methods, was strong up to the first 48h, though the target strain started getting in the death phase. The most sensitive bacteriocin is proven to be the one deriving from L.lactis, as it is partially loses its potency when heated in 80°C. These substances were proven to be sensitive when treated with in very high temperatures but are relatively stable. They maintain though their stability and potency even up to 72 h of storage.
.Discussion and Conclusion
When concentrated ,the bacteriocins were causing death of the target strain within 48h. They also retained their potency against the target strain for up to 60 h of storage. Treatment though with heat and microfiltration caused partial loss of potency, though the bacteriocin deriving from L.plantarum was proven to be most active. On the whole these substances were stable and there is potential to scale these processes for production knowing that if handled correctly they will not be significant losses."""

Biofermentation of otherwise called biotransformation process has been a heavily exploited and va... more Biofermentation of otherwise called biotransformation process has been a heavily exploited and vastly researched field of biochemical engineering science. Throughout the the years, especially during the last decades, a great number of of microbial groups has been tested for the production of commonly used chemicals. Due to the forecasted scarcity of petrol, an effort has been done to replace the production of chemicals deriving from petrochemical feedstocks, with fermentation. A group of bacteria that has being widely investigated due to their abilities are Lactic acifd Bacteria (LAB), especially Lactobacilli . These microorganisms have been widely used in today’s food, chemical and pharmaceutical industry.

These bacteria have numerous features, which are based on their main ability to ferment complex carbohydrates such as the production of acids, enzymes and natural antimicrobial substances called bacteriocins. Currently, they are principally used as natural acidifiers for the inoculation of bulk quantities of milk and vegetables in order to produce a variety of fermented products. some of the most important uses of Lactobacilli in the industry will be reviewed. The production of lactic acid and lantibiotics through the usage of modern fermentation technology, shall be highlighted

Keywords:Lactobacilly, LAB, fermentation science, biochemical engineering, industry, bacteriocins, lactic acid""

Spent digester effluents were formulated into nutrient media , suitable for microbial growth of i... more Spent digester effluents were formulated into nutrient media , suitable for microbial growth of industrially important microorganisms, using filtration and diafiltration. The waste effluents were pretreated by dilution, sedimentation and sieving for the removal of large particulate material. The scheme used allowed the successful formulation particle, free sterile effluents, with an N:P ratio 36.6 The prepared microfiltered effluents were then physicochemically characterized before being assessed for their utilization as growth substrates of microorganism associated with chemical and fuels production. Microfiltered treated digested propagated with Escherichia coli NCIMB 8277, agricultural sludge based media were compared with in vitro media when supplied with or without addition carbohydrate sources. in bench scale batch aerobic. Good growth was achieved compared to synthetic growth media with the microorganism using filtrates. When the treated effluents were supplied with 2 % w/v glucose solution a significant improvement in the growth rates and growth yields was achieved giving comparable performance with the synthetic media.

Keywords: microfiltration, anaerobic digestion, sludge, nutrient media, bacterial growth, biofuels, acid, wastewater treatment

Papers by Robert W Lovitt

CHISA2010 ECCE Conference Proceedings 2010 ISBN:987-80-02-02210-7, Sep 1, 2010

Lactobacilli belong to the group of lactic acid bacteria (LAB), widely used in the food industry ... more Lactobacilli belong to the group of lactic acid bacteria (LAB), widely used in the food industry nowadays. These microorganisms have several distinguishing abilities such as the production of lactic acid, enzymes such as β-galactosidase and natural antimicrobial substances called bacteriocins. They are mainly used as a natural acidifier for the inoculation of bulk quantities of milk and vegetables in order to produce a variety of fermented products. As such, large quantities of their biomass and the end products of their metabolism are necessary. The possibility of producing these substances in mass quantities will be investigated through several techniques. The selected Lactobacilli, L.plantarum NCIMB 8014, L.casei NCIMB 11970, L.lactis NCIMB 8586 and L.delbruckii NCIMB 11778 were grown into simple batch cultures without pH control where their physicochemical needs were determined. Through the determination of the optimum nutritional conditions for the propagation of the Lactobacilli, an optimised medium for growth occurred.
The growth efficiency on the medium was tested on a 2L STR reactor operated batch wise with continuous pH control. The optimum pH conditions for the growth of the bacilli were determined as well as parameters such as cellular yield coefficient, substrate and starter inoculum concentration and lactic acid rate and production. The metabolism of the Lactobacilli was determined as homofermentative, mainly producing lactic acid.
The efficiency of the optimized medium was evaluated in terms of growth rate and doubling time through the spectrophotometric measurement of cellular biomass.

Keywords: LAB, STR, Growth rate, Doubling time, lactic acid, nutrient medium

Proceedings ,Venice 2012, Fourth International Symposium on Energy from Biomass and Waste, Nov 12, 2012

Valuable nutrients can be recovered using filtration technology from complex waste effluent sourc... more Valuable nutrients can be recovered using filtration technology from complex waste effluent sources, allowing carbon based materials to be recycled and reused. Nutrients such as phosphate , ammonia and carboxylic acid can be directly applied in a wide range of fields in presents day industry including their use in the fertilizers production industry, textiles, cosmetics in the food industry. To address this challenge, effluents deriving from anaerobic digestion, were utilized for the recovery of these materials using filtration technology. This neutral process will consist a valuable carbon neutral waste processing strategy that is highly beneficial for the environment while providing industry with materials and reasonable cost.

Waste Management and the Environment VI pp:335-342 ISBN: 978-1-84564-606-6

The recovery of valuable nutrients, from waste sources allows carbon based materials to be recycl... more The recovery of valuable nutrients, from waste sources allows carbon based materials to be recycled and reused through the production of organic materials. For example, phosphate and ammonia, can be directly applied in a wide range of fields in today’s industrial world including their use in the fertilizers production industry, textiles, cosmetics in the food industry. The aim of this research is the ability to recover these sources from waste processes, such as anaerobic digestion and promote these materials in the industry. These neutral processes will provide valuable carbon neutral processes that are highly beneficial for the environment as provide industry with materials and reasonable cost.

Keywords: waste process, nutrients, particle size, dry matter, ammonia, phosphate, environment, conductivity, salinity, sludge""

http://dx.doi.org/10.1016/j.apcbee.2012.06.010 ICBFS 3rd International Conference on Biotechnology and Food Science

A great number of Gram (+) and Gram negative (-) bacteria produce during their growth, substances... more A great number of Gram (+) and Gram negative (-) bacteria produce during their growth, substances of protein structure (either proteins or polypeptides) possessing antimicrobial activities, called bacteriocins. Although bacteriocins could be categorized as antibiotics, they are not. The major difference between bacteriocins and antibiotics is that bacteriocins restrict their activity to strains of species related to the producing species and particularly to strains of the same species, antibiotics on the other hand have a wider activity spectrum and even if their activity is restricted this does not show any preferential effect on closely related strains. In addition, bacteriocins are ribosomally synthesized and produced during the primary phase of growth, though antibiotics are usually secondary metabolites. Among the Gram (+) bacteria, lactic acid bacteria (LAB) especially, Lactobacilli have gained particular attention nowadays, due to the production of bacteriocins. These substances can be applied in the food industry as natural preservatives. The use of LAB and of their metabolic products is generally considered as safe (GRAS, Grade One). The application of the produced antimicrobial compounds as a natural barrier against pathogens and food spoilage caused by bacterial agents has been proven to be efficient. Nisin is the only bacteriocin that has been officially employed in the food industry and its use has been approved worldwide. Bacteriocins can be applied on a purified or on a crude form or through the use of a product previously fermented with a bacteriocin producing strain as an ingredient in food processing or incorporated through a bacteriocin producing strain (starter culture).
Keywords: Lactic acid bacteria, Lactobacilli, Bacteriocins, Nisin, Plantaricins, Lantibiotics

DOI: 10.1007/s12602-012-9102-2, Apr 18, 2012

Three Lactobacilli strains, Lactobacillus casei NCIMB 11970, Lactobacillus plantarum NCIMB 8014, ... more Three Lactobacilli strains, Lactobacillus casei NCIMB 11970, Lactobacillus plantarum NCIMB 8014, Lactobacillus lactis NCIMB 8586 have been used for the production of bacteriocins. Though, their production phase, their biochemical nature, their mode of activity even their genetic structure have been widely investigated, there are hardly any studies investigating their potency and activity in depth of time, in other words their shelf life under several physicochemical conditions that may occur during their production in large scale. As such, the effect of several factors influencing the activity and the potency of bacteriocins when produced in large scale was examined as due to bacteriocins peptide nature degradation or denaturation might occur, under extreme physicochemical conditions. During scale-up process, differences between the output data may occur, such as concerning biomass, metabolic by-products and limiting substrate concentrations. These may affect negatively the activity and the potency of the bacteriocins. For investigating these effects and minimizing them, numerous studies were conducted, which were related to the exact phase of the production of these substances, the effect of dilution and temperature changes. These studies could be used in order to minimize the scaling-up effect when decided to produce these peptides in large scale.

Book of Abstracts 8th Green Chemistry Conference An International Event Deposito Legal: Z-3507-2009, 2009

Keywords: LAB, STR, Growth rate, Doubling time, lactic acid, nutrient medium.

DOI: 10.7763/IJCEA.2010.V1.10

Lactobacilli belong to the group of lactic acid bacteria (LAB), widely used in the food industry ... more Lactobacilli belong to the group of lactic acid bacteria (LAB), widely used in the food industry nowadays. These microorganisms have several distinguishing abilities such as the production of lactic acid, enzymes such as β-galactosidase and natural antimicrobial substances called bacteriocins. They are mainly used as a natural acidifier for the inoculation of bulk quantities of milk and vegetables in order to produce a variety of fermented products. As such, large quantities of their biomass and the end products of their metabolism are necessary. The possibility of producing these substances in mass quantities will be investigated through several techniques. The selected Lactobacilli, L.plantarum NCIMB 8014, L.casei NCIMB 11970, L.lactis NCIMB 8586were grown into simple batch cultures without pH control where their physicochemical needs were determined. Through the determination of the optimum nutritional conditions for the propagation of the Lactobacilli, an optimised medium for growth occurred. The optimum pH conditions for the growth of the bacilli were determined as well as parameters such as cellular yield coefficient, substrate and starter inoculums concentration and lactic acid rate and production. The metabolism of the Lactobacilli was determined as homofermentative, mainly producing lactic acid. The efficiency of the medium combining al the optimised parameters, enhancing the productivity biomass and therefore bacteriocins production from the strains, was tested on a 2L STR reactor operated batch wise with continuous pH control. A simple liquid turbidometric method was developed to test the bacteriocin productivity of the selected bacteria. The activity and potency of the bacteriocin produced was tested against L.delbruckii subsp.lactis NCIMB 8117.
Index Terms-Doubling time, Growth rate, Lactic acid, Nisin

Engineering Our Future: Are We up to the Challenge? pp:1830-1838 ISBN: 9780858259225

Lactobacilli belong to the group of lactic acid bacteria (LAB), widely used in the food industry ... more Lactobacilli belong to the group of lactic acid bacteria (LAB), widely used in the food industry These microorganisms have several distinguishing abilities such as the production of lactic acid, enzymes such as β-galactosidase and natural antimicrobial substances called bacteriocins. They are mainly used as a natural acidifier for the inoculation of bulk quantities of milk and vegetables in order to produce a variety of fermented products. As such, large quantities of their biomass and the end products of their metabolism are necessary. The possibility of producing these substances in mass quantities was investigated through several techniques. Selected Lactobacilli, L.plantarum NCIMB 8014, L.casei NCIMB 11970, L.lactis NCIMB 8586 and L.delbruckii NCIMB 11778 were grown into batch cultures without pH control where their physicochemical needs were determined. Through the determination of the optimum nutritional conditions for the propagation of the Lactobacilli, an optimised medium for growth was developed. The efficiency of the medium was tested in a 2L STR reactor operated batch wise with continuous pH control. The optimum pH conditions for the growth of the bacilli were determined as well as parameters such as cellular yield coefficient, substrate and starter inoculum concentration and lactic acid rate and production. The metabolism of the Lactobacilli was determined as homofermentative, mainly producing lactate. Efficiency of the optimized medium was evaluated in terms of growth rate and doubling time through the spectrophotometric measurement of cellular biomass. The medium strongly supports the growth of the Lactobacilli giving a growth rate between 0.22 to 0.32 h-1

Keywords: LAB, STR, Growth rate, Doubling time, lactic acid, nutrient medium.

Proceedings of 2010 International Conference on Chemical Engineering and Applications (CCEA 2010) pp:13-18 ISBN: 978-1-84626-023-0

Fermentation technology has been a widely researched and exploited field of the science of biotec... more Fermentation technology has been a widely researched and exploited field of the science of biotechnology. Through out the recent years the vast majority of microbial groups have been tested for the production of beneficial compounds especially for the replacement of products produced by petrol such as lactic acid. A bacterial group that heavily attracts attention due to its products are Lactic Acid Bacteria (LAB) and especially Lactobacilli. Lactobacilli are widely used in the food and pharmaceutical industry nowadays. These microorganisms have several distinguishing features based on their main ability to ferment carbohydrates such as the production of acids, enzymes and natural antimicrobial substances called bacteriocins. They are mainly used as natural acidifiers for the inoculation of bulk quantities of milk and vegetables in order to produce a variety of fermented products. As such, large quantities of their biomass and the end products of their metabolism are necessary. In this article some of the most important uses of Lactobacilli in the industry will be reviewed. Emphasis will be given in the production of lactic acid, β-galactosidase and lantibiotics through the usage of modern fermentation technology.
Keywords: LAB, fermentation technology, food industry, β-galactosidase, lactic acid.

Proceedings,Venice 2012, Fourth International Symposium on Energy from Biomass and Waste,ISBN:978-88-6265-006-9, Nov 12, 2012

"Volatile fatty acids (VFA) including acetic, butyric, formic and propionic are extensively utili... more "Volatile fatty acids (VFA) including acetic, butyric, formic and propionic are extensively utilized in contemporary industry. Their commercial value is of high significance while their often derive from petroleum which is non-abundance source. Other methods for the production and recovery from these substances have been proposed and investigated. Waste effluent streams are potential candidates for VFA recovery, especially if for their processing filtration technology will be used. Membrane filtration is an effective and efficient choice as it is a low cost, low energy, easy integrated method tested for the separation and concentration.
"

http://dx.doi.org/10.1016/j.procbio.2013.05.017

Current separation, isolation and purification techniques to obtain highly potent purified lacto... more Current separation, isolation and purification techniques to obtain highly potent purified
lactobacilli and lactococcoi bacteriocins include chemical precipitation, separation employing solvents
and chromatographic techniques. These methods are arduous, costly, with limited scalability, offering
low bacteriocin yields (<20%). To address these challenges, the alternatives of ultrafiltration and
nanofiltration, as separation methods were tested. Three promising bacteriocin producing strains,
Lactobacillus casei NCIMB 11970, Lactobacillus plantarum NCIMB 8014 and Lactococcus lactis NCIMB
8586 were selected to investigate the applicability and feasibility of the method.
To facilitate separation, the microorganisms were grown on specially developed low molecular weight
medium (LMWM) mainly containing nutritive sources up to 4 kDa molecular weight. Bacterial cells
were removed by centrifugation. The clarified broths were filtered using 4 and 1 kDa MWCO.
Bacteriocin activity was determined by an antimicrobial activity test using nisin, which has an
inhibitory effect on the growth of susceptible microorganisms. Recovery yields using filtration were
found to range between 53 to 68%, a high recovery performance.
The bacteriocin activity of crude extracts of all the three lactobacilli were between 95-105 IU ml-1.
When the substances were separated using ultrafiltration membrane (4kDa MWCO) their activity was
enhanced to 145-150 IU ml-1, achieving a total potency yield of 44% to 53%. Further enhancement of
yields up to 36% was attained employing nanofiltration (1 kDa MWCO) membranes with an activity
increased up to 200 IU ml-1.
Bacteriocin isolation from crude extracts using filtration was found to be effective, offering high
recovery yields, optimizing their activity as well as presenting a realistic option towards the
formulation of these as commercially available antibacterial agents.

DOI: 10.1007/s13213-012-0581-x, Dec 20, 2012

An economic liquid growth medium was synthesised for high-rate production of cellular mass, lacti... more An economic liquid growth medium was synthesised for high-rate production of cellular mass, lactic acid and bacteriocin in lactobacilli. Three lactobacilli that are applied extensively in industry—Lactobacillus casei NCIMB 11970, Lactobacillus plantarum NCIMB 8014, Lactobacillus lactis NCIMB 8586—were chosen to test the medium’s efficiency. These bacteria are chemoorganotrophs requiring rich, complex media for optimum growth. Contrary to the current practice of formulating a strain-specific medium, we attempted to prepare a universal broth that would allow easy formulation and optimisation. Man de Rogosa Sharp (MRS) medium, which can support the growth of lactobacilli, was found unsuitable for use in large quantities due to its high cost of preparation and its use of beef extract and peptone from poultry as nitrogen sources, which are not environmentally friendly and have potential health risks. The developed medium supported the growth of all the three bacteria equally, offering good maximum yields and incorporating only the chemical compounds needed, resulting in an improvement in the growth rate of the bacilli of between 50 % and 241 % compared to the same strains grown on MRS. Lactic acid production was between 28.6 and 35.74 g L−1 and bacteriocin production ranged from 110 to 130 IU mL−1.

DOI: 10.1007/s12649-013-9202-6, Feb 13, 2013

The recovery of volatile fatty acids (VFA), from complex effluent streams deriving from numerous ... more The recovery of volatile fatty acids (VFA), from complex effluent streams deriving from numerous sources has been an area of research interest for more than a century. In the current era, technological and economic development is widely based on the limited global petroleum resources. Regardless the scarcity faced in coal based fuels, VFA are still extensively and in most cases solely, synthesised from petroleum. With the constantly rising
awareness of the environmental impact the carbon based economy has created, research has been focused in
developing alternative methods of their production. These include fermentation, anaerobic digestion and recovery
from discharged chemical and industrial plants effluents.
During these processes, the hydrolysis of target solid wastes followed by the microbial conversion of them to
biodegradable organic, content results in the production of intermediate VFA, commonly acetate and butyrate.
These, are detected at varying concentrations in the effluent streams and mixed liquors of the reactor systems. Their
concentration is depending on hydraulic, retention and organic loading rates. Several studies have shown possible environmental and commercial benefits using various techniques for their separation and recovery. Among these, extensively applied has been reactive extraction. Currently, membrane
filtration is most prominent as a source separation process in comparison to integral wastewater treatment.
VFA reclamation benefits include the formulation of a valorisized waste effluent that can be further processed for the recovery of valuable nutrients, the relief of municipal treatment plants and the recycle and re-use of favorable nutrients and chemicals."

"In the present study, a monolithic alumina coated microfiltration ceramic membrane was used for ... more "In the present study, a monolithic alumina coated microfiltration ceramic membrane was used for solid particulates removal and nutrients recovery from anaerobic digester complex effluent streams. The aim was to test the effect of the cake layer developed by the solids, on the surface of the membrane channels, to the filterability of these materials. The solids content ranged between 2.6 g/L to 15.1 g/L. During practical application, two processing techniques targeting the enhanced recovery of the materials of interest including ammonia, phosphate, calcium bicarbonate and volatile fatty acids, namely dewatering and diafiltration, were used. These had an immediate effect on the solids content (PDS 13μm to 3.97μm) enhancing the filterability of the effluents. Their processability was evaluated in terms of flux, cross flow velocity, membrane resistance and cake resistance. Important findings of this study is the nonalignment of the flux rates to the cake resistance, explained by the formation of a compressible, permeable cake layer that allowed the continuous operation of the system, under constant low pressure conditions (TMP 15 psi). Permeate flux remained constant to 120 L/m2 h when applying diafiltration, while when dewatering process is used the permeate flux remained constant at 115.4 L/m2 h.
Keywords: sludge; ceramic filter; cake resistance; flux; cross flow filtration"

Microbes in Applied Research: Current Advances and Challenges pp: 321-326 Editor: A. Mendez-Vilas ISBN: 978-981-4405-03-4 , Aug 2012

Lactobacilli belong to the group of Lactic Acid Bacteria (LAB), widely used in the dairy industry... more Lactobacilli belong to the group of Lactic Acid Bacteria (LAB), widely used in the dairy industry nowadays. These bacteria are used as a natural acidifier, for the inoculation of bulk quantities of milk and vegetables, in order to produce a variety of fermented products. As such, large quantities of their biomass are necessary. In addition, during their growth, they naturally produce antimicrobial substances, called bacteriocins. Due to the constantly developing need for natural food preservatives, bacteriocin function and activity has been extensively investigated.
The possibility of producing these substances in mass quantities will be investigated through several techniques. Three carefully selected Lactobacilli, L.plantarum NCIMB 8014, L.casei NCIMB 11970 and L.lactis NCIMB 8586 were grown into simple batch cultures without pH control, where their physicochemical needs were determined. Through the determination of the optimum nutritional conditions for their propagation an optimised growth medium occurred. A simple, liquid turbidometric method was developed to test the bacteriocin productivity of these strains. The antimicrobial activity and potency of the bacteriocins produced, were tested against the target strain L.delbruckii subsp.lactis NCIMB 8117.
The optimised medium was then filtrated via membrane modules of 4 and 30 kDa , in an effort to simplify the medium and facilitate the extraction of the produced substance. The medium’s efficiency in supporting the growth and the bacteriocin production of the bacilli was tested and comparative studies between filtrated and unfiltrated media were done.

Keywords: LAB, Bacteriocins, Target strain, Ultrafiltration, Growth rate, Doubling time""

Analytical Methods, 2014

ABSTRACT Biofouling is a crucial issue, and it causes seawater reverse osmosis membrane to deteri... more ABSTRACT Biofouling is a crucial issue, and it causes seawater reverse osmosis membrane to deteriorate the performance of desalination. In this study, excitation emission matrix (EEM) fluorescence spectroscopy and parallel factor analysis (PARAFAC) were used to monitor the strength of biofouling on the fouled membrane which was obtained from real plant. Based on EEM and PARAFAC results of raw seawater, feed water, permeate, brine and fouled membrane, three components were identified as the major peaks: (1) microbial product-like materials at Ex/Em = 280/370 nm, (2) humic-like substances at Ex/Em = 330/420 nm, and (3) aromatic proteins at Ex/Em = 240/320 nm. Using the fluorescence intensity changes, the effects of replacing fouled RO membranes were found to be most significant at one of the components (Ex/Em = 270-300/350-380 nm) which could be considered the substances desorbed from fouled RO membrane. Compared to the data for salt rejection, this component monitoring of the brine EEM image is shown to be more sensitive than conductivity monitoring for predicting the biofouling strength during the desalination process.