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The isolation of nanocellulose from different agricultural residues is becoming an important research field due to its versatile applications. This work collects different production processes, including conditioning steps, pretreatments, bleaching processes and finally purification for the production of nanocellulose in its main types of morphologies: cellulose nanofiber (CNF) and cellulose nanocrystal (CNC). This review highlights the importance of agricultural wastes in the production of nanocellulose in order to reduce environmental impact, use of fossil resources, guarantee sustainable economic growth and close the circle of resource use. Finally, the possible applications of the nanocellulose obtained as a new source of raw material in various industrial fields are discussed.

The fermentation of mixtures of D-glucose and D-xylose by three non-traditional yeasts: Candida shehatae (ATCC 34887), Pachysolen tannophilus (ATCC 32691) and Pichia stipitis (ATCC 58376) have been studied to determine the optimal strain and initial culture conditions for the ef®cient production of ethanol. The comparison was made on the basis of maximum speci®c growth rate (m m ), biomass productivity, the speci®c rates of total substrate consumption (q s ) and ethanol production (q E ) and the overall yields of ethanol and xylitol. All the experiments were performed in stirred-tank batch reactors at a temperature of 30°C. The initial pH of the culture medium was 4.5. The highest values of m m (above 0.5 h À1 ) were obtained with P stipitis in cultures containing high concentrations of D-xylose. All three yeasts consumed the two monosaccharides in sequence, beginning with D-glucose. The values of q s diminished during the course of each experiment with all of the yeasts. The highest values of the speci®c rates of total substrate consumption and ethanol production were obtained with C shehatae (for t = 10 h, q s and q E were above 5 g g À1 h À1 and 2 g g À1 h À1, respectively), although the highest overall ethanol yields were fairly similar with all three yeasts, at around 0.4 g g À1.

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