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Abstract:The commercial inulinase obtained from Aspergillus niger was non-covalently immobilized on multiwalled carbon nanotubes (MWNT-COOH). The immobilization conditions for the carbon nanotubes were defined by the central composite rotational design (CCRD). The effects of enzyme concentration (0.8%-1.7% v/v) and adsorbent:adsorbate ratio (1:460-1:175) on the enzyme immobilization were studied. The adsorbent:adsorbate ratio variable has positive effect and the enzyme concentration has a negative effect on the inulinase immobilization (U/g) response at the 90% significance level. These results show that the lower the enzyme concentration and the higher the adsorbent:adsorbate ratio, better is the immobilization. According to the results, it is possible to observe that the carbon nanotubes present an effective inulinase adsorption. Fast adsorption in about six minutes and a loading capacity of 51,047 U/g support using a 1.3% (v/v) inulinase concentration and a 1:460 adsorbent:adsorbate ratio was observed. The effects of temperature on the immobilized enzyme activity were evaluated, showing better activity at 50 °C. The immobilized enzyme maintained 100% of its activity during five weeks at room temperature. The immobilization strategy with MWNT-COOH was defined by the experimental design, showing that inulinase immobilization is a promising biotechnological application of carbon nanotubes.

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The diffusion of photovoltaic distributed generation is relevant for addressing the political, economic, and environmental issues in the electricity sector. However, the proliferation of distributed generation brings new administrative and operational challenges for the sustainability of electric power utilities. Electricity distributors operate in economies of scale, and the high photovoltaic penetration means that these companies have economic and financial impacts, in addition to influencing the migration of other consumers. Thus, this paper aims to systematically identify and evaluate critical factors and indicators that may influence electricity distributors in predicting their consumers' adoption of photovoltaic technology, which were subjected to the analysis of 20 industry experts. Results show that the cost of electricity, generation capacity, and cost of the photovoltaic systems are the most relevant indicators, and it is possible to measure a considerable part of them using the internal data of the electricity distributors. The study contributes to the understanding of the critical factors for the forecast of the adoption of consumers to distributed photovoltaic generation, to assist the distribution network operators in the decision making, and the distribution sustainability. Also, it establishes the theoretical, political, and practical implications for the Brazilian scenario and developing countries.