Amanda Laca

Development of a structure-based model for the competitive growth of Listeria innocua in minced chicken breasts.

Most predictive models are based on planktonic microbial growth in broth and, therefore, do not deal with diffusional limitations generated by the solid-food structure. Recently, a few approaches have incorporated the diffusional component, but still on the basis of pure cultures growing in homogenous supports. In this work, a transport-phenomenon model that considers the complex and dynamic structure of real foods, as well as its background microflora, has been developed. This structure-based model was applied to the competitive growth of Listeria innocua in minced chicken breasts, considering oxygen as the limiting substrate. Physical structure and microbial growth in minced meat were compared to those reported for meat-based kappa-carrageenan gels by means of scanning electron microscopy (SEM) and viable counts. In both systems, microbial growth was affected by diffusional limitations, as compared with broth cultures. However, significant differences in their physical structure and a key effect of the indigenous microflora and the meat tissue itself, resulted in different extent and distribution of microbial growth. The approach here developed, useful for food safety purposes, has been shown to provide a reasonably good simulation of experimental data in minced breasts.

Stirring and Mixing Effects at Different Cider Fermentation Scales

When fermentations are carried out without mechanical agitation, mixing will depend on the C02 bubbles released during the process. This parameter may, therefore, also substantially influence the ’observed’ kinetics of the process due to the existence of different local rates and mass transfer phenomena. This paper is a study of autoinduced and mechanical agitation powers in cider fermentation processes at different scales. The influence of the scale-up on the main process parameters has also been analysed.

Eggshell waste as catalyst: A review

Agricultural wastes are some of the most emerging problems in food industries because of their disposal cost. However, it is also an opportunity for the bioeconomy society if new uses for these residual materials can be found. Eggshells, considered a hazardous waste by UE regulations, are discarded, amounting hundreds of thousands of tonnes worldwide. This egg processing waste is a valuable source material, which can be used in different fields such as fodder or fertilizer production. Additionally, this residue offers interesting characteristics to be used in other applications, like its employment as an environment-friendly catalyst. In the present review we provide a global view of eggshell waste uses as catalyst in different processes. According to reviewed researching works, a huge variety of added value products can be obtained by using this catalyst which emphasised the interest of further investigations in order to widen the possible uses of this cheap green catalyst.

Mixed cultures of Serratia marcescens and Kluyveromyces fragilis for simultaneous protease production and COD removal of whey

Aims:  The aim of this study was to investigate the behaviour of a Serratia marcescens–Kluyveromyces fragilis mixed culture in whey, with the objective of proteases production and organic waste reduction.

Treatment of supermarket vegetable wastes to be used as alternative substrates in bioprocesses

Fruits and vegetables have the highest wastage rates at retail and consumer levels. These wastes have promising potential for being used as substrates in bioprocesses. However, an effective hydrolysis of carbohydrates that form these residues has to be developed before the biotransformation. In this work, vegetable wastes from supermarket (tomatoes, green peppers and potatoes) have been separately treated by acid, thermal and enzymatic hydrolysis processes in order to maximise the concentration of fermentable sugars in the final broth. For all substrates, thermal and enzymatic processes have shown to be the most effective. A new combined hydrolysis procedure including these both treatments was also assayed and the enzymatic step was successfully modelled. With this combined hydrolysis, the percentage of reducing sugars extracted was increased, in comparison with the amount extracted from non-hydrolysed samples, approximately by 30% in the case of tomato and green peeper wastes. For potato wastes this percentage increased from values lower than 1% to 77%. In addition, very low values of fermentation inhibitors were found in the final broth.

UNDERSTANDING THE SIMULTANEOUS BIODEGRADATION OF THIOCYANATE AND SALICYLIC ACID BY PARACOCCUS THIOCYANATUSAND PSEUDOMONAS PUTIDA

Phenolic and cyanide compounds, which frequently appear mixed in several industrial effluents, are difficult to be biodegraded under certain conditions. In this work, salicylic acid (SA) and thiocyanate (SCN−) were selected as model pollutants of these two families and experiments of biodegradation with specific microorganisms were developed. It was found that the best well-known bacteria able to biodegrade each one of these pollutants, Pseudomonas putida for SA and Paracoccus thiocyanatus for SCN−, do not biodegrade the other one. Therefore, the co-culture was required, producing interesting interaction phenomena. When both pollutants were simultaneously biodegraded, a commensalism effect was observed improving SCN− removal. Experimental data for SCN− and SA removals were successfully fitted to zero reaction kinetic orders, with induction time in the case of SCN−, and substrate dependences were fitted to Tessier models. A flow cytometry method was developed and employed to obtain the evolution of the viable, damaged and dead cells for different substrate concentration and the degree of agglomeration in the co-culture experiments.

Microbial diversity on commercial eggs as affected by the production system. A first approach using PGM

A novel DNA-based technique (PGM) has been employed for first time to analyse commercial eggs with the advantage of allowing an exhaustive identification of the microbiota present. Eggs from two different production systems, i.e. a free range system and a cage system, were analysed. Twenty-one and twenty-two phyla were identified on the surface of cage system and free range system eggs, respectively. In both cases, Firmicutes was the dominant phylum (representing around 50% of total phyla), being found families frequently reported to be present in the intestinal microbiota of chickens or hens, such as Clostridiaceae, Ruminococcaceae and Lachnospiraceae. Additionally, other phyla and families not previously described in association with eggshells could also be identified in this work. Most of the potential pathogenic genera associated with eggs (Salmonella, Clostridium, Helicobacter, Pseudomonas and Staphylococcus) showed higher incidence in eggs coming from cage systems than in eggs coming from free range systems, although the abundance of these genera were very low in both cases (<5% of total bacteria).

Gels prepared from egg yolk and its fractions for tissue engineering

New biomaterials prepared from egg yolk and its main fractions (plasma and granules) have been developed for use in tissue engineering. Protein gels obtained via transglutaminase cross‐linking were characterized by rheometry, texturometry and scanning electron microscopy. All the gels exhibited suitable physical and mechanical characteristics for use as potential biomaterials in skin regeneration. Specifically, results showed that these materials presented a compact, uniform structure, with granular gel being found to be the most resistant as well as the most elastic material. Accordingly, these gels were subsequently evaluated as scaffolds for murine fibroblast growth. The best results were obtained with granule gels. Not only adhesion and cell growth were detected when using these gels, but also continuous coatings of cells growing on their surface. These findings can be attributed to the higher protein content of this fraction and to the particular structure of its proteins. Thus, granules have proved to be an interesting potential raw material for scaffold development.

Environmental impact of cheese production: A case study of a small-scale factory in southern Europe and global overview of carbon footprint

The environmental performance of a small-scale cheese factory sited in a NW Spanish region has been analysed by Life Cycle Assessment (LCA) as representative of numerous cheese traditional factories that are scattered through the European Union, especially in the southern countries. Inventory data were directly obtained from this facility corresponding to one-year operation, and the main subsystems involved in cheese production were included, i.e. raw materials, water, electricity, energy, cleaning products, packaging materials, transports, solid and liquid wastes and gas emissions. Results indicated that the environmental impacts derived from cheese making were mainly originated from raw milk production and the natural land transformation was the most affected of the considered categories. On the contrary, the manufacturing of packaging material and other non-dairy ingredients barely influenced on the total impact. Additionally, an average carbon footprint of the cheeses produced in the analysed facility has also been calculated, resulting milk production and pellet boiler emissions the most contributing subsystems. Furthermore, it was notable the positive environmental effect that entailed the direct use of whey as animal feed, which was considered in this study as avoided fodder. Finally, a revision of published works regarding the environmental performance of cheese production worldwide was provided and compared to results found in the present work. According to the analysed data, it is clear that the content of fat and dry extract are determinant factors for the carbon footprint of cheeses, whereas the cheesemaking scale and the geographical area have a very low effect.

Diffusion and Inhibition Processes in a Hollow-fiber Membrane Bioreactor for Hybridoma Culture. Development of a Mathematical Model

The performance of a hollow-fiber membrane bioreactor (HFBR) (molecular weight cut-off 30 kD, fiber surface area 2050 cm2) containing a culture of hybridoma cells has been investigated. Experimental data were used as basis to develop a model of general application. Concentrations of fundamental nutrients (glucose and glutamine), inhibitory products (ammonium and lactate), and monoclonal antibodies (MAb) against bovine lactoferrin (IgG1) were monitored over time. Exchange of nutrients and products occurred across the capillary surface, whereas cells and MAb remained in the extra-capillary space (ECS). A protein-free culture medium (Hybrimax) with and without antibiotics was used. In both cases, the final MAb concentration was the same; however, antibiotic presence slowed down the time to achieve this concentration. Diffusion assays have been carried out in order to support the development of a mathematical model that describes the performance of the HFBR, including mass transfer and reaction terms. Inhibition by ammonium and lactate has been considered in the kinetics, providing model results consistent with experimental data. Further research with other cell lines and/or culture media will allow to broaden the field of application of this model for general use in HFBR systems.