Keilla S. Cerqueira

Microalgae have a high growth rate, high CO₂ absorption capacity, and high content of chlorophyll, proteins, vitamins, mineral salts, carbohydrates, antioxidant substances, and fatty acids. In recent years, Chlorella vulgaris has been widely used as a feedstock for producing third-generation biofuels, such as bioethanol. Thus, this work aims to develop a strategy to increase the production scale of the microalgae Chlorella vulgaris grown in distilled reused water, supplemented with a modified BG-11 medium, to use biomass in the production of bioethanol. The total cultivation of 72 L presented a concentration of 0.415 g·L⁻¹·d⁻¹, with 61.32 g of final biomass. To improve carbohydrate extraction, the biomass was pre-treated with sulfuric acid at different concentrations (1.5% and 3% v/v). The hydrolyzed solution was supplemented with YPD (yeast extract peptone dextrose) medium and inoculated with Saccharomyces cerevisae yeast, initiating fermentation. In each sample, the Brix degree, cell concentration, reducing sugar concentration, and alcohol content were analyzed. The sample pre-treated with sulfuric acid 1.5% v/v was the one that presented the best result, with alcohol content after distillation of 68 °GL (Gay-Lussac). It appears that the cultivation of the microalgae Chlorella vulgaris in scale-up, with reused water, has high potential in the production of third-generation biofuel.

Enzymes have several applications and potential, in addition to being an alternative for industry because they have advantages over synthetic chemicals that release polluting and toxic by-products into the environment. The optimization of the production of enzymes that degrade cellulose is of great interest, and in order to increase the viability of its use, several studies have been selecting sources and identifying means of obtaining and evaluating the enzymatic activity of these enzymes. Microorganisms can be used in the recycling of waste or in the production of several products with high added value, including biomolecules of industrial importance. The low cost of this raw material allows the development of economically competitive and ecological processes. Coconut fiber is an abundant lignocellulosic material and a rich source of cellulose, hemicellulose, and lignin, presenting itself as a promising and low-cost raw material for the production of enzymes. This work aims to produce endoglucanase from microorganisms isolated from coconut fiber to produce second-generation ethanol. For this, the kinetic profile of the enzymatic complex containing cellulases was evaluated, analyzing the effects of moisture content, temperature, and pH during the solid-state fermentation of coconut fiber, using a microorganism isolated from the bagasse itself. The Statistica software was used to evaluate the enzyme's complex production parameters through Pareto charts and response surface plotting. The statistical results indicated that the best conditions of humidity, temperature, and pH were 80%, 30°C, and 3 with activities of 182 U/g endoglucanase in a time of 168 h.