João Moreira Neto

Adsorption characteristics of cellulase and β-glucosidase on Avicel, pretreated sugarcane bagasse, and lignin

Although adsorption is an essential step in the enzymatic hydrolysis of lignocellulosic materials, literature reports controversial results in relation to the adsorption of the cellulolitic enzymes on different biomasses/pretreatments, which makes difficult the description of this phenomenon in hydrolysis mathematical models. In this work, the adsorption of these enzymes on Avicel and sugarcane bagasse pretreated by the hydrothermal bagasse (HB) and organosolv bagasse (OB) methods was evaluated. The results have shown no significant adsorption of β‐glucosidase on Avicel or HB. Increasing solids concentration from 5% (w/v) to 10% (w/v) had no impact on the adsorption of cellulase on the different biomasses if stirring rates were high enough (>100 rpm for Avicel and >150 rpm for HB and OB). Adsorption equilibrium time was low for Avicel (10 Min) when compared with the lignocellulosic materials (120 Min). Adsorption isotherms determined at 4 and 50 °C have shown that for Avicel there was a decrease in the maximum adsorption capacity (Emax) with the temperature increase, whereas for HB increasing temperature increased Emax. Also, Emax increased with the content of lignin in the material. Adsorption studies of cellulase on lignin left after enzymatic digestion of HB show lower but significant adsorption capacity (Emax = 11.92 ± 0.76 mg/g).

Nanotechnology Applications on Lignocellulosic Biomass Pretreatment

Global population growth raises questions concerning the environment and energy production. Fossil fuels are well known and utilized energy source. These are not renewable and contribute to the greenhouse gas effect. The search for alternative energy sources and solution for environmental problems has a growing concern in recent years. The lignocellulosic biomass has emerged as a solution to our energy and environmental concerns since it is rich within feedstock and can be converted to biofuels and/or biomaterials. This approach is interesting because these biomasses can become renewable sources of energy and pollute less than fossil fuels when transformed into biofuels, which is a green fuel. However, some steps are necessary to transform these lignocellulosic biomasses into biofuels or biomaterials. Nanotechnology is a multidisciplinary area of study with several applications that can be used to improve the lignocellulose bioconversion process, used both in production of liquid fuels through conversion by fermentation, gasification, or catalysis and development of new nanoscale catalyzers/materials. Nanoscale or sub-nanoscale instrumentation facilitates understanding of the lignocellulosic biomass cell wall ultrastructure and enzymatic mechanisms. This aspect contributes in the development of sophisticated instrumentation techniques for lignocellulosic fiber analysis such as scanning electronic microscopy (SEM), transmission electronic microscopy (TEM), and atomic force microscopy (AFM).

Silver: Biomedical Applications and Adverse Effects

Silver metal has been used by humanity for about 7000 years. The use of this metal was observed in objects such as coins and cutlery that was used due to the corrosion resistance of this noble metal. Due to slow corrosion, the silver ions are continuously released from the materials. Silver is a metallic transition element, which has a shiny and white appearance. This metal can be found widely in the human environment. The use of silver in various branches of medicine has increased significantly as antibacterial, antiviral, antimycotic, and chemotherapeutic agents. In addition, this metal is very effective in medical devices, textile, cosmetic, and even household appliance. Silver can act as a drug in its most varied forms, whether in ionic, colloidal, combined, or nanoparticle form, this element has demonstrated potential in a series of treatments of diseases, including cancer, malaria, and inflammation, mainly in the uterine region. Silver can also be used in the treatment of wounds, burns, presenting high potential as human medication. The therapeutic potential of metal complexes in the treatment of cancer has attracted interest because the metals have peculiar characteristics (redox activity, modes of variable coordination, and reactivity in relation to the organic substrate). In addition, although silver may have an adverse effect on the body and the environment, if used in an excessive concentration. But, if used in an ideal concentration, it may be a good approach for current medicine.

Measurements of Mode Conversion Co-Efficients in Multimode Optical Fibres

In order to assess quantitatively the quality of optical fibres we are now producing routinely in our laboratories, we have carried out preliminary measurements, with a very simple system, and calculated the normalized mode conversion co-efficient (D). The values of D obtained are of the order of 2 × 10-5 rad-2 m-1 for our fibres and these compare very favourably with the results obtained in other laboratories.