Biotecnologia

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Navegando Biotecnologia por Assunto "Activated charcoal"

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    Reduction of the enzyme loading for hydrolysis of alkaline pretreated green coconut husk
    (Universidade Federal do Espírito Santo, 2019-05-23) Bolivar Telleria, Maria; Fernandes, Antônio Alberto Ribeiro; Fernandes, Patrícia Machado Bueno; Santos, Alexandre Martins Costa; Tussell, Raúl Tapia
    Coconut (Coco nucifera) is a crop largely produced by tropical countries for its water and meat. This represents a handling and environmental issue as an estimated of 46 million tons of waste in the form of coconut husks is produced each year. Different alternatives to obtain added-value products from this waste have been studied, including the production of ethanol. One of the most expensive steps on the ethanol production process with this kind of substrates is the enzymatic hydrolysis due to the high cost of the enzymes used. Unfortunately, green coconut husk has a high lignin content, which inhibits the enzymes and leads to the use of high enzyme loading increasing the production cost. The detoxification of the hydrolysates prior to enzymatic hydrolysis and the addition of polymers, proteins and surfactants have proven to decrease the inhibition of the enzymes improving the enzymatic hydrolysis. This enzymatic hydrolysis enhancement enables the reduction of enzyme loading, leading to a process with higher economic viability. The purpose of this study is to reduce the enzyme loading used for the hydrolysis of alkaline pretreated green coconut husk by using different additives. First, the detoxification of the alkaline pretreated green coconut husk slurry with activated charcoal was evaluated. The direct and indirect (inside a pouch) addition of the activated charcoal showed a decrease in acetic acid concentration but also in fermentable sugars concentration. No benefit was seen at the end of the process while adding activated charcoal. In addition, the use of activated charcoal heavily inhibited the fermentation. Successively, the direct addition of casein or PEG to the alkaline pretreated green coconut husk slurry to enhance the enzymatic hydrolysis without a detoxification step was tested. The addition of casein showed an improvement on the hydrolysis but not on the results for the overall process. On the other hand, the addition of PEG helped improve the enzymatic hydrolysis and results from the overall process under some of the conditions tested. Initially, the enzymatic hydrolysis with the addition of different concentrations of PEG4000 (0.010, 0.025 or 0.050 g/g bm) using three enzyme loadings (3.0, 5.0 or 7.5 FPU/g bm) was performed. The use of 0.050 g PEG4000/g bm enabled to obtain the best results using a low enzyme loading of 5.0 FPU/g bm. Subsequently, the addition of PEGs with various chain lengths was examined, using 0.050 g PEG/g bm and 5.0 FPU/g bm. PEG4000 presented better results than PEG8000 and the PEG mixture (15,000 and 20,000 g/mol). Furthermore, the hydrolysates containing PEG4000 were fermented to monitor ethanol production. No inhibition was observed for the hydrolysates of alkaline pretreated green coconut husk treated with PEG4000. The addition of PEG4000 proved to be a viable procedure to decrease the enzyme loading used during enzymatic hydrolysis of alkaline pretreated green coconut husk to produce ethanol by 66.7%.