On-line monitoring of citric acid production in solid-state culture by respirometry

6 páginas, 4 figurasThe aim of this work was to study the possibility of monitoring citric acid production from mussel processing wastes (MPW) by Aspergillus niger in solid-state culture (SSC) on an inert support. This was conducted by measuring CO2 and 02 concentration in exhaust gases, using an automatic sampler connected to a gas chromatograph and a data acquisition system. The procedure permitted information on the physiological state of the culture to be obtained. A relationship between citric acid accumulation and a decreasc in CO, production was found, allowing citric acid production to be followed in real-time. Moreover, respiratory activity (p,.) can be estimated and the effect of different variables on this parameter studied. Initial nitrogen concentration, a critical factor for achieving high production of citric acid from MPW in submerged culture. revealed no effect in SSC. This indicates a tolerance of SSC to higher concentrations of nitrogen constituting an advantage when using residual media with high levels of protein and wlriability in their composition.J. Pintado thanks the Galician Government, Xunta de Galicia, for a research grantPeer reviewe

Evaluation of laccase production for Pleurotus spp

International audienc

Spatio-temporal analysis of post-harvest moulds genera distribution on stored durum wheat cultivated in Tunisia

Wheat represents a principal ingredient in traditional Tunisian diet including couscous, bread, pasta and biscuits. Northen Tunisia is an important growing area of wheat which after harvest is stored in silos and on farm. The cereal grains can become contaminated by post-harvest moulds during storage in silos under unfavorable conditions leading to a decrease in quality, packing and marketing of wheat. In this study, a mycological survey was undertaken to determine the biodiversity of post-harvest moulds on durum wheat stored in silos localized in five regions of Northern Tunisia and to investigate changes during the storage period. A total of 127 samples were obtained from Oued Mliz, Jendouba, Ksar Mezouar, Mateur and Ghezala silos during 2010-2011 and 2011-2012 wheat seasons. After sampling, seeds were placed on Potato Dextrose Agar medium (PDA) for 7 days of incubation at 28 degrees C. A total of 6035 strains of filamentous fungi were isolated. The quantitative and qualitative changes on wheat mycoflora during storage were statistically explored by multivariate methods including correspondence and hierarchical cluster analysis. The most predominant post-harvest moulds genera isolated were Alternaria (28%), Fusarium (19%), Penicillium (19%), Aspergillus (14%), Mucor (8%) and Rhizopus (7%). Various genera of fungi imperfecti, including Ulocladium, Geotrichum, Chaetomium, Trichothecium, Paecilomyces, Aureobasidium and Chrysonilia (anamorphic Neurospora), and the Mucorales genera Lichtheiia and Syncephalastrum accounted for the remainder of about 6% of the total. Statistical data analysis revealed six mycological patterns corresponding to six distinct communities as characterized by the prevalence of different moulds. Such patterns clearly showed different spatio-temporal variability indicating that distribution and evolution of moulds during storage was sensitive to geographic location, year of sampling and short or long-term storage

Lactic acid bacteria against post-harvest moulds and ochratoxin A isolated from stored wheat

A total of 54 lactic acid bacteria (LAB) were isolated from stored wheat samples sourced from grain silos in North Tunisia. Fifteen representative isolates were identified by 16S rDNA sequencing as Pediococcus pentosaceus, Lactobacillus plantarum, Lactobacillus graminis, Lactobacillus coryniformis and Weissella cibaria. These isolates were screened for antifungal activity in dual culture agar plate assay against eight post-harvest moulds (Penicillium expansum, Penicillium chrysogenum, Penicillium glabrum, Aspergillus flavus, Aspergillus niger, Aspergillus carbonarius, Fusarium graminearum and Alternaria alternata). All LAB showed inhibitory activity against moulds, especially strains of L. plantarum which exhibited a large antifungal spectrum. Moreover, LAB species such as L plantarum LabN10, L. graminis LabN11 and P. pentosaceus LabN12 showed high inhibitory effects against the ochratoxigenic strain A. carbonarius ANC89. These LAB were also investigated for their ability to reduce A. carbonarius ANC89 biomass and its ochratoxin A (OTA) production on liquid medium at 28 and 37 degrees C and varied pH conditions. The results indicated that factors such as temperature, pH and bacterial biomass on mixed cultures, has a significant effect on fungal inhibition and OTA production. High percentage of OTA reduction was obtained by L. plantarum and L. graminis (>97%) followed by P. pentosaceus (>81.5%). These findings suggest that in addition to L. plantarum, L graminis and P. pentosaceus strains may be exploited as a potential OTA detoxifying agent to protect humans and animals health against this toxic metabolite

Robusta coffee beans post-harvest microflora : Lactobacillus plantarum sp as potential antagonist of Aspergillus carbonarius

Coffee contamination by ochratoxigenic fungi affects both coffee quality as well as coffee price with harmful consequences on the economy of the coffee exporting countries for whom which is their main source of income. Fungal strains were isolated from coffee beans and identified as black Aspergilli. Ochratoxigenic moulds like Aspergillus carbonarius were screened and selected for detailed studies. Also lactic acid bacteria (LAB) were isolated from silage coffee pulp and their antifungal activity was tested on dual-culture agar plate. Ten of the isolated LAB demonstrated antifungal effect against A. carbonarius. API 50 CH and APIZYM were used to perform phenotypic identification. 16S rDNA sequencing was made to confirm the results

Phenolic compounds from coffee and olive and their main biotechnological potentialities

International audienc

Phenolic compounds from coffee and olive and their main biotechnological potentialities

International audienc

Dietary utilisation of protein and energy from fresh and ensiled coffee pulp by the Nile tilapia, Oreochromis niloticus

Dietary protein and energy utilisation of diets containing fresh and ensiled coffee pulp were studied on 3.2 ± 0.2 g Nile tilapia for 28 days. Diets formulation and feeding were designed on the basis of daily dietary protein and energy allowance. A control diet A (100 % protein and 100 % energy allowance) corresponding to 15 g CP kg-1 day-1 and 750 kJ kg-1 day-1, a low protein control diet B (80 % protein and 100 % energy allowance), two diets C and E (100 % protein and 100 % energy allowance) where 20 % of protein were supplied by coffee pulp, and two diets D and F with the same amount of coffee pulp than in C and E and supplementation in non-protein energy. Inclusion of coffee pulp in the diet strongly impaired growth and feed utilisation. Silage process improved overall feed utilisation comparing to fresh coffee pulp. Results showed that fresh or ensiled coffee pulp was not a suitable feedstuff for Nile tilapia. However, better knowledge on modification occurring during silage process could allow finding the way to significantly improve nutritive value of coffee pulp by-products.<br>Polpa de café ensilada foi utilizada na dieta calórica-protéica de Tilápia do Nilo na razão de 3.2 g ± 0,2 durante um período de 28 dias. As dietas calórico-protéica foram formuladas com base na ingestão diária permitida. Uma dieta A controle (100% de proteína e 100% da energia) que corresponde a g PC/kg/dia e 750 Kj/Kg/dia, uma dieta B baixa em proteína (80% de proteína e 100% da energia), duas dietas C e E (100% de proteína e 100% da energia) onde 20% da proteína foi suplementada com polpa de café e duas dietas D e F com a mesma concentração de polpa de café é prejudicial a dieta de crescimento. O processo de ensilagem melhorou sua utilização como alimento em comparação com a polpa de café fresca. Os resultados demonstraram que a polpa fresca ou ensilada não é para ser usada como alimentação de Tilápia do Nilo. Entretanto, uma melhor conhecimento do processo de ensilagem da polpa de café pode ser uma via importante para aumentar o valor nutritivo da polpa de café