Ana B. Díaz

Evaluation of microwave-assisted pretreatment of lignocellulosic biomass immersed in alkaline glycerol for fermentable sugars production

A pretreatment with microwave irradiation was applied to enhance enzyme hydrolysis of corn straw and rice husk immersed in water, aqueous glycerol or alkaline glycerol. Native and pretreated solids underwent enzyme hydrolysis using the extract obtained from the fermentation of Myceliophthora heterothallica, comparing its efficiency with that of the commercial cellulose cocktail Celluclast®. The highest saccharification yields, for both corn straw and rice husk, were attained when biomass was pretreated in alkaline glycerol, method that has not been previously reported in literature. Moreover, FTIR, TG and SEM analysis revealed a more significant modification in the structure of corn straw subjected to this pretreatment. Highest global yields were attained with the crude enzyme extract, which might be the result of its content in a great variety of hydrolytic enzymes, as revealed zymogram analysis. Moreover, its hydrolysis efficiency can be improved by its supplementation with commercial β-glucosidase.

Alkaline and alkaline peroxide pretreatments at mild temperature to enhance enzymatic hydrolysis of rice hulls and straw.

The current study explores alkaline and alkaline peroxide pretreatments in order to achieve a method to improve saccharification of agricultural residues for ethanol production. The effects of reagent concentration and pretreatment time at 30°C and atmospheric pressure on biomass dissolution after the pretreatment and enzymatic hydrolysis of the pretreated biomass were investigated. In fact, although all pretreatments tested improved enzymatic hydrolysis of native residues, the best results were not achieved for the highest biomass loss. The maximum conversions to reducing sugars in the hydrolysis stage of 77.5% and 92.6% were obtained for rice hulls and straw pretreated by alkaline peroxide (4%, 24h) and alkaline (1%, 48 h) methods, respectively. For both pretreated residues, the reduction to more than half the recommended enzyme loading allowed obtaining more than 94% the reducing sugars attained with the recommended dose.

Xylanase production by Aspergillus awamori under solid state fermentation conditions on tomato pomace

Inthiswork,� tomatopomace,� awasteabundantlyava ilableintheMediterraneanandothertemperate� climatesagrofoodindustries,�hasbeenusedasraw �materialfortheproductionofsomehydrolyticenz ymes,� includingxylanase,�exopolygalacturonase�(exoPG), �cellulase�(CMCase)�and�α�amylase.�Theprincipalst ep� oftheprocessisthesolidstatefermentation�(SSF )�ofthisresiduebyAspergillus awamori.�Inseveral� laboratoryexperiments,�maximumxylanaseandexoPG �activitiesweremeasuredduringthefirstdaysof�

Comparison of industrially viable pretreatments to enhance soybean straw biodegradability.

This study explores acid and alkaline pretreatments in order to enhance soybean straw biodegradability. The effects of sulfuric acid and sodium hydroxide for different pretreatment times at 30°C and 121°C on biomass dissolution and the subsequent enzymatic hydrolysis were investigated. The highest total conversion to reducing sugars of 93.9% was attained when soybean straw was pretreated with acid (4% H2SO4, 121°C, 1 h) and subsequently subjected to the enzymatic process. However, conversion of 86.5%, were reached only with the hydrolysis of the pretreated residue using mild conditions, (0.5% NaOH, 30°C, 48 h), involving the reduction cost of the process. In addition to this, this result was dramatically decreased when pectinase was removed from the enzyme cocktail. It has been also demonstrated that the reduction of the enzyme loading to less than half allowed obtaining about 96% of the reducing sugars attained with the highest enzyme dose.

Modelling of different enzyme productions by solid-state fermentation on several agro-industrial residues.

A simple kinetic model, with only three fitting parameters, for several enzyme productions in Petri dishes by solid-state fermentation is proposed in this paper, which may be a valuable tool for simulation of this type of processes. Basically, the model is able to predict temporal fungal enzyme production by solid-state fermentation on complex substrates, maximum enzyme activity expected and time at which these maxima are reached. In this work, several fermentations in solid state were performed in Petri dishes, using four filamentous fungi grown on different agro-industrial residues, measuring xylanase, exo-polygalacturonase, cellulose and laccase activities over time. Regression coefficients after fitting experimental data to the proposed model turned out to be quite high in all cases. In fact, these results are very interesting considering, on the one hand, the simplicity of the model and, on the other hand, that enzyme activities correspond to different enzymes, produced by different fungi on different substrates.

Valorization of exhausted sugar beet cossettes by successive hydrolysis and two fermentations for the production of bio-products

Exhausted sugar beet cossettes (ESBC) show an enormous potential as a source of sugars for the production of bio-products. Enzyme hydrolysis with the combined effect of mainly cellulases, xylanases and pectinases, turned out to be very efficient, obtaining almost double the concentration of sugars measured with the sole action of Celluclast® and β-glucosidase, and increasing 5 times the hydrolysis rate. As the sole pretreatment, ESBC soaked in the hydrolysis buffer were autoclaved, avoiding the application of severe conventional biomass pretreatments. Moreover, a promising alternative for the complete utilization of glucose, xylose, arabinose, mannose and maltose contained in ESBC is proposed in this paper. It consists of sequential fermentation of sugars released in the hydrolysis step to produce bioethanol and lactic acid as main bio-products. Compared to separate fermentations, with this strategy glucose and hemicellulose derived sugars were completely consumed and the 44% of pectin derived sugars.

Status and Perspectives in Bioethanol Production From Sugar Beet

Abstract The chemical composition of sugar beet roots makes this raw material an attractive feedstock for ethanol fermentation. In the manufacture of sugar from this crop, various intermediates, by-products, and wastes are generated, which can be used for the production of energy and other value-added products, such as biofuels. In this chapter, the current processes for the conversion of the sugary juices (raw, thin, and thick juices), molasses and sugar beet pulp into bioethanol are described. In addition, the economics of sugar beet ethanol and the principal strategies proposed for increasing bioethanol yields are described.