D. Mamma

An alternative approach to the bioconversion of sweet sorghum carbohydrates to ethanol

The ethanol fermentation of juice and press cake, resulting from the squeezing of sweet sorghum stalks at high pressure, was investigated. The juice was fermented by Saccharomyces cerevisiae and yielded 4.8 g ethanol per 100 g of fresh stalks. The press cake was fermented directly to ethanol by a mixed culture of Fusarium oxysporum and Saccharomyces cerevisiae and yielded 5.1 g ethanol per 100 g of fresh stalks. An overall ethanol concentration and yield of 5.6% (w/v) and 9.9 g of ethanol per 100 g of fresh stalks respectively was obtained. Based on soluble carbohydrates, the ethanol yield from press cake was doubled while the overall theoretical yield was enhanced by 20.7% due to the bioconversion of a significant portion of cell wall polysaccharides to ethanol. The process was found promising for further investigation.

Bioethanol from sweet sorghum: Simultaneous saccharification and fermentation of carbohydrates by a mixed microbial culture

Sweet sorghum carbohydrates were simultaneously saccharified and fermented to ethanol by a mixed culture of Fusarium oxysporum and Saccharomyces cerevisiae in a bioreactor. Fusarium oxysporum was grown aerobically for the production of the enzymes necessary for the saccharification of sorghum cellulose and hemicellulose. Saccharomyces cerevisiae, together with F. oxysporum, converted the soluble sugars to ethanol. Three batches of sorghum were used, harvested at different periods of the year. The optimum yield of bioconversion and ethanol concentration was 5·2–8·4 g ethanol/100 g of fresh sorghum and 3·5–4·9% (w/v), respectively, depending on the composition of sorghum stalks. In all experiments, the ethanol yield exceeded the theoretical, based on soluble sugars, by 20·0–32·1% due to bioconversion of polysaccharides to ethanol.

Hemicellulolytic activity of Fusarium oxysporum grown on sugar beet pulp. Production of extracellular arabinanase.

Fusarium oxysporum F3 exhibited hemicellulolytic enzymic activity when grown on sugar beet pulp, a by-product of the sugar industry. The growth medium was specifically optimised for enhanced production of extracellular arabinanase. The optimum medium contained sugar beet pulp (4%, w/v) and corn steep liquor (6%, v/v) as carbon and nitrogen sources, respectively. Arabinanase activity as high as 0.25 U/ml of culture was obtained, which compared favourably to those reported for other microorganisms. Optimal arabinanase activity was observed at pH 6–7 and 50°C. Investigation of the degradation of the main components of sugar beet pulp showed that arabinose containing polysaccharides and pectin were first degraded, followed by the glucose-containing polysaccharides.

Enhanced acetyl esterase production by Fusarium oxysporum

Production of acetyl esterase (EC 3.1.1.6) by Fusarium oxysporum strain F3 was enhanced by optimization of growth conditions. Under optimal conditions, activities as high as 0.89u2009U/ml of culture medium were obtained. The culture filtrate was equally active on p-nitrophenyl acetate and acetylxylan. The enzyme produced 71% deacetylation of acetylxylan in 2u2009h at 40u2009∘C. Activity was optimized at pH6.5 and at 55u2009∘C. The respective Km values for p-nitrophenyl acetate and acetylxylan were 0.25u2009mM and 1.05% (w/v) and the Vm values were 0.65 and 0.43u2009μmol acetate/min/mg protein.

Production of an esterase from Fusarium oxysporum catalysing transesterification reactions in organic solvents

Abstract The production of an esterase by Fusarium oxysporum , grown on tomato skins as the sole carbon source, was studied in submerged and solid state cultures. Under optimum growth conditions, enzyme yields as high as 7·3 U/ml of culture medium and 19·4 U/g of carbon source were obtained. The esterase catalysed the synthesis of esters in organic solvents. Geraniol was transacetylated in hexane by the esterase using triacetyl as an acetyl donor. The geranyl acetate yield was 68%.

Catechol 1,2-dioxygenase from Pseudomonas putida in organic media : an electron paramagnetic resonance study

The ability of an isolated isozyme of catechol 1,2-dioxygenase from Pseudomonas putida DSM 437 to function in a non-aqueous environment was investigated. The lyophilized enzyme is able to keep its catalytic function catalyzing the oxidation of catechol in n-hexane. Electron paramagnetic resonance (EPR) spectroscopy at liquid helium temperatures was applied to compare the properties of the non-heme iron of the enzyme in the organic solvent and in the aqueous solution. The catalytic performance of the enzyme in the organic solvent is correlated with the spectroscopic properties of the non-heme iron.

INNOVATIVE CONCEPTS IN AGRICULTURAL RESIDUES UTILISATION FOR SUSTAINABLE DEVELOPMENT IN DEVELOPING COUNTRIES (ICARUS)

ABSTRACT This work focuses on the innovative concept of the bioconversion of agricultural resources by Simultaneous Saccharification and Fermentation Process (SSF). Presently SSF is applied in bioresources from Greece, Nigeria and P.R. China. The most promising results were achieved with sweet sorghum which was converted into ethanol by mixed cultures of Fusarium oxysporum and yeast.