Browsing by Author "Manso, Teresa"
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- Carob pulp as raw material for production of the biocontrol agent P. agglomerans PBC-1Publication . Manso, Teresa; Nunes, Carla; Raposo, Sara; Lima-Costa, Maria EmíliaLarge-scale production has been the major obstacle to the success of many biopesticides. The spreading of microbial biocontrol agents against postharvest disease, as a safe and environmentally friendly alternative to synthetic fungicides, is quite dependent on their industrial mass production from low-cost raw materials. Considerable interest has been shown in using agricultural waste products and by-products from food industry as nitrogen and carbon sources. In this work, carob pulp aqueous extracts were used as carbon source in the production of the biocontrol agent Pantoea agglomerans PBC-1. Optimal sugar extraction was achieved at a solid/liquid ratio of 1:10 (w/v), at 25°C, for 1 h. Batch experiments were performed in shake flasks, at different concentrations and in stirred reactors at two initial inoculums concentrations, 106 and 107 cfu ml−1. The initial sugar concentration of 5 g l−1 allowed rapid growth (0.16 h−1) and high biomass productivity (0.28 g l−1 h−1) and was chosen as the value for use in stirred reactor experiments. After 22 and 32 h of fermentation the viable population reached was 3.2 × 109 and 6.2 × 109 cfu ml−1 in the fermenter inoculated at 106 cfu ml−1 and 2.7 × 109 and 6.7 × 109 cfu ml−1 in the bioreactor inoculated at 107 cfu ml−1. A 78% reduction of the pathogen incidence was achieved with PBC-1 at 1 × 108 cfu ml−1, grown in medium with carob extracts, on artificially wounded apples stored after 7 days at 25°C against P. expansum.
- Development and application of a SCAR marker to monitor and quantify populations of the postharvest biocontrol agent Pantoea agglomerans CPA-2Publication . Nunes, Carla; Bajji, Mohammed; Stepien, Valerie; Manso, Teresa; Torres, Rosario; Usall, Josep; Jijakli, M. HaissamPantoea agglomerans CPA-2 is an effective biocontrol agent of postharvest diseases of citrus and pome fruit. A monitoring technique was developed for its identification and to quantify its populations. The methodology used consisted of (i) searching for a semi-selective medium, (ii) identification of molecular markers and (iii) monitoring population dynamics in a commercial trial. As a semi-selective medium, Malonate Broth Agar supplemented with tetracycline hydroxychloricle and incubation at high temperature (max. of 40 degrees C) facilitated the selective recovery of P agglomerans CPA-2 colonies. The RAPD technique was applied to a collection of 13 strains of P. agglomerans, including CPA-2. Among the 12 primers tested, OPL-11 amplified a fragment (about 720 bp) specific to strain CPA-2. On the basis of this fragment, two SCAR markers were amplified using a primer pair derived from OPL-11 elongation. A first SCAR marker of 720 bp was specifically amplified for the strain CPA-2 and a second one of 270bp was obtained for all P. agglomerans strains tested, including CPA-2. Commercial trials demonstrated a significant reduction of decay with the treatment of formulated cells of R agglomerans CPA-2. Population dynamics of CPA-2 in commercial trials were determined on fruit surfaces and in the environment using both the classical plating technique and PCR with SCAR primers. In general, no significant differences were observed between results obtained from the two methods. On fruit surfaces, 1 day after CPA-2 applied its population by classical methods was 4.37 x 10(6) cfu wound(-1) and at the end of the experiment the population increased to 5.8 x 10(5) cfu wound(-1). The percentages of colonies identified as P agglomerans CPA-2 at these sampling times using SCAR primers were 90 and 95%, respectively. Population dynamics in the environment to evaluate the environmental fate of R agglomerans CPA-2 showed that it has a limited persistence and limited capacity for dispersion. (c) 2007 Published by Elsevier B.V.
- Effect of electrolyzed water as a disinfectant for fresh-cut fruitPublication . Graça, Ana; Salazar, Miguel; Quintas, Célia; Manso, Teresa; Nunes, Carla; Nunes, CarlaIn fresh-cut processing the disinfection is the most important step. This process can affect the quality and the safety of the end product as well as its shelf life. Chlorine is the most used disinfectant in fresh-cut industry but due to its association with environmental and health risks, the development of alternative sanitizers is emergent. Electrolyzed water (EW) may be an alternative to the use of chlorine sanitizers and both acidic electrolyzed water (AEW) and neutral electrolyzed water (NEW) can be used with this purpose. In fact, several studies have shown that EW can be effective in reducing pathogenic bacteria on the surface of fruits and vegetables. This manuscript presents a review of electrolyzed water approaches, its antimicrobial activity in fresh-cut produce and the results of a study undertaken in our laboratory to evaluate the disinfection efficacy of AEW and NEW on fresh-cut apples and oranges. Fresh-cut apples and fresh cut oranges were inoculated with a suspension of Listeria innocua and fresh-cut oranges with Escherichia coli at a concentration of 107 cfu mL-1 and treated with the different solutions. Untreated freshcut fruits were used as control. The best sanitizing treatment for both pathogens and fruits was AEW at 200 ppm of free chlorine applied during 5 minutes.
- Production of the biocontrol agent Pantoea agglomerans PBC-1 in a stirred tank reactor by batch and fed-batch culturesPublication . Manso, Teresa; Nunes, Carla; Raposo, Sara; Lima-Costa, Maria EmíliaConcerns about food safety as well as the development of resistance to many fungicides by major postharvest pathogens have increased recently. Biological control, using microorganisms antagonistic to the fungal plant pathogens, appears to be promising as an alternative to fungicides. The microbial biocontrol agent has to be produced on an industrial scale, maintaining its biocontrol efficacy. The purpose of the current study was to optimize the conditions for microbial biomass production of the biocontrol agent Pantoea agglomerans PBC-1 in a 2-l mechanically stirred reactor (STR), defining mixing and mass transfer technological parameters and the growth kinetics for different saccharides. In the batch mode, different impellers and spargers were tested. Despite the oxygen mass transfer improvement achieved with marine propeller combined with porous sparger, the biomass did not increase, if compared with the use of a Rushton turbine and L-sparger, pointing out the relevance of a radial flux for better broth homogenization. Different carbon sources were used: sucrose, glucose and fructose; each of which led to viable populations 3.9 × 109, 1.4 × 109, 3.9 × 109 c.f.u/ml, respectively, after 20 h of incubation. Fed-batch technology allows the maintenance of high cell viability for longer periods of time in the stationary growth phase, which can be crucial for the scale-up of biocontrol agent production process that is achieved together with a reduction of 85% on the incidence caused by the pathogens, brought about by fresh microbial biomass preparation on artificially wounded apples or oranges, stored for 7 days at 25°C against Penicillium expansum and Penicillium digitatum.
- Study of modes of action of the biocontrol agent metschnikowia and auensis pbc-2Publication . Manso, Teresa; Vero, Silvana; González, M. Belén; Nunes, Carla; Nunes, CarlaMetschnikowia andauensis NCYC 3728 (PBC-2) is an effective antagonist against the postharvest pathogens Penicillium expansum, Botrytis cinerea and Rhizopus stolofiner on pome fruits, however its mode of action is unknown. The ability of this strain to produce inhibitory compounds in 4 distinct media (PDA, NYDA, YPDA, CJA) at 3 temperatures (1, 25, 30 ºC), was investigated. It was also assayed the competition for iron in media with different iron concentrations and characterized the capability of PBC-2 produce and secrete fungal cell wall lytic enzymes, like chitinase, protease, and glucanase in a culture media with fungal pathogen cell wall as unique carbon source. M. andauensis PBC-2 did not show any inhibition zone to cope pathogens in any of the tested media. The results obtained in this study suggest that the production and secretion of lytic enzymes is not the main or more important mode of action of the new biocontrol agent PBC-2, since the production of chitinase was observed only past 5 and 7 d of incubation, and the production of -1.3-glucanases and proteases was not observed, which mean that the biocontrol agent PBC-2 have more than one mechanism of action.
- Sustainable bioethanol production using agro-industrial by-productsPublication . Pardão, J.; Diaz, I.; Raposo, Sara; Manso, Teresa; Lima-Costa, Maria EmíliaThis work aimed to evaluate a sustainable bioethanol production by a laboratorial isolate strain of Saccharomyces cerevisiae, along with the use of agro-industrial by-products as carbon source. The effect of several carbon sources and their concentrations was studied using carob pod extract (CPE) and beet molasses (BM) and compared with glucose and sucrose as conventional carbohydrates at different concentrations, 15, 20 and 30 g/l.No significant difference was found between maximum ethanol production obtained with CPE, BM, glucose and sucrose fermentations profiles. It was obtained values of 10.65 g/l and 10.5 g/l ethanol, respectively for sucrose and CPE at 30g/l, which can be improved using higher substrate concentration.