Abstract Biotechnology can be used to convert waste into valuable products. In this context, there is bacterial cellulose (BC), a natural biopolymer that can be transformed into several useful materials, but its production is limited due to the high cost of the culture media used for its industrialization. In this work, BC was produced from the bacteria Komagataeibacter rhaeticus, using coffee grounds, sugarcane molasses and ethanol. The experiments were carried out under static conditions. The products were collected every 48 h, with a total period of 240 h. The maximum BC production (11.08 g.L-1) was obtained in a culture medium supplemented with coffee powder, hydrolyzed cane molasses and the addition of 1% (v/v) ethanol. The results show that the use of different carbon sources of the evaluated by-products are viable alternatives in reducing costs in BC production.

Sugarcane bagasse fibers chemically modified on its surface were used to adsorb contaminants from biodiesel. Two biodiesel samples were used as adsorbates: crude and washed biodiesel. The contaminants were mainly glycerol and water, but also ions, and methanol. The biodiesel is usually washed, in order to remove most of the contaminants, but the procedure introduces large amounts of water, which are further difficult to remove, because the biodiesel acting as an acceptor of hydrogen bond. The adsorbent used in this work was proved to be very efficient to remove the contaminants and also to remove water from the washing the crude biodiesel. The contaminants adsorbed from biodiesel were identified by thermal analyses (DSC and DTA) of the fibers (adsorbent) and of the biodiesel (adsorbate) by comparing the results with the pure biodiesel. The proportion of free glycerol showed high adsorption efficiency for the crude biodiesel. A total amount of 1.34 g of fibers was estimated as being needed for its complete removal. The mass of bagasse fibers added (up to 1g) in a fixed volume of biodiesel was a relevant condition, as the saturation in fibers started at around 0.70 g cleaning up to about 98% removal of the impurities.