RESUMEN
AIMS: In this study, we have investigated the biochemical behaviour of Aspergillus sp. (five strains) and Penicillium expansum (one strain) fungi cultivated on waste cooking olive oil. The production of lipid-rich biomass was the main target of the work. In parallel, the biosynthesis of other extracellular metabolites (organic acids) and enzyme (lipase) and the substrate fatty acid specificity of the strains were studied. METHODS AND RESULTS: Carbon-limited cultures were performed on waste oil, added in the growth medium at 15g l(-1) , and high biomass quantities were produced (up to c.18g l(-1) , conversion yield of c. 1·0 g of dry biomass formed per g of fat consumed or higher). Cellular lipids were accumulated in notable quantities in almost all cultures. Aspergillus sp. ATHUM 3482 accumulated lipid up to 64·0% (w/w) in dry fungal mass. In parallel, extracellular lipase activity was quantified, and it was revealed to be strain and fermentation time dependent, with a maximum quantity of 645 U ml(-1) being obtained by Aspergillus niger NRRL 363. Storage lipid content significantly decreased at the stationary growth phase. Some differences in the fatty acid composition of both cellular and residual lipids when compared with the initial substrate fat used were observed; in various cases, cellular lipids more saturated and enriched with arachidic acid were produced. Aspergillus strains produced oxalic acid up to 5·0 g l(-1) . CONCLUSIONS: Aspergillus and Penicillium strains are able to convert waste cooking olive oil into high-added-value products. SIGNIFICANCE AND IMPACT OF THE STUDY: Increasing fatty wastes amounts are annually produced. The current study provided an alternative way of biovalourization of these materials, by using them as substrates, to produce added-value compounds.
Asunto(s)
Aspergillus/metabolismo , Microbiología Industrial/métodos , Lípidos/biosíntesis , Penicillium/metabolismo , Aceites de Plantas/química , Eliminación de Residuos Líquidos/métodos , Aspergillus/crecimiento & desarrollo , Biomasa , Reactores Biológicos , Biotecnología/métodos , Culinaria , Medios de Cultivo , Fermentación , Lipasa/metabolismo , Aceite de Oliva , Penicillium/crecimiento & desarrollo , Especificidad por SustratoRESUMEN
AIMS: To investigate the effect of organic nitrogen on lipogenesis during growth of Cunninghamella echinulata on tomato waste hydrolysate (TWH) media. METHODS AND RESULTS: Cunninghamella echinulata grown on a TWH medium rapidly took up glucose and produced large amounts of lipids. However, when some quantities of the organic nitrogen were removed from TWH (by acid followed by alkaline precipitation of proteins) the uptake of glucose was dramatically reduced and large quantities of fungal biomass having low lipid content were produced. Nevertheless, when glycerol was used as carbon source instead of glucose, the uptake rate as well as the biomass production and the lipid accumulation processes were unaffected by the TWH organic nitrogen removal. Finally, when the fungus was grown on a glucose supplemented TWH medium that contained no assimilable organic nitrogen (after further precipitation of proteins with methanol), the produced biomass contained non-negligible quantities of lipids, although glucose uptake remained low. Lipid analysis showed that the produced lipids comprised mainly of neutral lipids, which were preferentially consumed during lipid turnover. Lipid production on the original TWH medium having glucose as carbon source was 0.48 g of lipid per gram of dry biomass, corresponding to 8.7 g of lipid per litre of growth medium. The produced lipids contained 11.7%gamma-linolenic acid (GLA), hence the GLA yield was more than 1 g l(-1). CONCLUSIONS: Organic nitrogen compounds found in TWH favour glucose (but not glycerol) uptake and lipid accumulation in C. echinulata. SIGNIFICANCE AND IMPACT OF THE STUDY: Agro-industrial wastes containing organic nitrogen, such as tomato waste, are produced in vast amounts causing severe environmental problems. These wastes could be used as fermentation feedstock to produce microbial lipids.
Asunto(s)
Cunninghamella/crecimiento & desarrollo , Microbiología de Alimentos , Glucosa/metabolismo , Metabolismo de los Lípidos , Nitrógeno/farmacología , Solanum lycopersicum/metabolismo , Biomasa , Reactores Biológicos/microbiología , Carbono/metabolismo , Cromatografía en Capa Delgada/métodos , Medios de Cultivo , Cunninghamella/metabolismo , Ácidos Grasos/metabolismo , Fermentación , Lípidos/análisis , Nitrógeno/metabolismoRESUMEN
The polymorphic fungus Aureobasidium pullulans ATHUM 2915, produced significant quantities of extracellular polygalacturonase and polysaccharide when grown, under controlled conditions, in liquid medium with pectin and glucose as carbon sources and nitrogen source as limited factor. Growth, substrate consumption and products formation were simulated by a structured mathematical model, which was compared with the experimental data from batch culture in a chemostat. This model was applied successfully in the study of some essential parameters influenced the process at various pH values.
Asunto(s)
Hongos Mitospóricos/metabolismo , Poligalacturonasa/biosíntesis , Polisacáridos/biosíntesis , Biomasa , Carbono/análisis , Medios de Cultivo , Glucosa/metabolismo , Concentración de Iones de Hidrógeno , Hongos Mitospóricos/enzimología , Hongos Mitospóricos/crecimiento & desarrollo , Modelos Teóricos , Nitrógeno/análisis , Pectinas/metabolismoRESUMEN
A wild type of Aspergillus sp. ATHUM-3482 produced extracellular polygalacturonase when grown in liquid medium containing citrus pectin as sole carbon source. A number of factors affecting enzyme activity were investigated. Polygalacturonase activities as high as 4.3 U ml-1 (reducing-group-releasing activity) and 17 U ml-1 (viscosity-diminishing activity) were obtained under optimum growth conditions. With sugar-beet as sole carbon source the respective activities were 6.5 U ml-1 and 40 U ml-1, the highest achieved in this work. Under these conditions no pectin lyase or pectinesterase activity was detected. The above yields of polygalacturonase activity compare favourably with those reported for fungi grown under similar growth conditions.