Production of laccase for the pre-treatment of anaerobic digestion of wastewater from coffee processing

Author(s)

Fabricio Soares Moreira

• Document type: Master's Dissertation
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Escola de Engenharia de São Carlos (EESC/SBD)
• Defense date: 2024-02-09

Examining board members

Giovana Tommaso; Mirian Yasmine Krauspenhar Niz; Vera Maria Valle Vitali

• Advisor: Giovana Tommaso

Abstract

Coffee has great commercial importance for Brazil, which is considered the largest producer and exporter of coffee in the world. The processing of all this production is responsible for the generation of large quantities of wastewater. Coffee processing wastewater (CPWW) is difficult to degrade as it contains a large amount of organic matter and toxic components and, therefore, there is a need to develop economically viable solutions for managing this waste before its disposal. Therefore, the present work proposed the use of CPWW as a substrate for the production of ligninolytic enzymes by basidiomycete fungus, and the use of these enzymes in the pre-treatment of wastewater from coffee processing simulated on a bench for pre-treatment of anaerobic digestion. Among the stages of this research were: 1. evaluation of growth of the fungus Pleurotus ostreatus in CPWW in solid state; 2. optimization of P. ostreatus enzyme production using sequential experimental designs; 3. characterization of the laccase enzyme present in the enzyme extract; 4. optimization of the degradation of CPWW components by the enzymatic extract (pre-treatment); 5. determination of the anaerobic biodegradability of pre-treated wastewater and wastewater without pre-treatment, with comparison of the processes through the estimation of kinetic parameters of methane production. The tolerance of P. ostreatus to CPWW was evaluated in solid medium containing CPWW, P. ostreatus was able to grow in all concentrations of CPWW, in addition to discoloring ARBC undiluted. The optimization of laccase enzyme production in CPWW by P. ostreatus, in vivo, in liquid medium was evaluated using two experimental designs: Plackett Burman (PB) and Factorial Design (PF). The PB indicated that the concentrations of CuSO4, MnSO4 and agitation were the variables that most positively influenced laccase production by P. ostreatus. In PF, only CuSO4 was statistically significant for laccase production, at a 95% confidence level. After choosing the laccase production condition, laccase production kinetics was carried out for 30 days to determine the main enzyme production peaks. The enzymatic extract obtained at the peak of laccase production was characterized in physical-chemical parameters and used for the pre-treatment of wastewater produced on the bench, optimized from a 23 factorial design, in which the pH and agitation were statistically significant, pH has a negative effect and agitation has a positive effect, in relation to the removal of phenolic compounds. The test selected in pre-treatment of CPWW was studied with anaerobic biodegradability in comparison with CPWW without pre-treatment, it was found that enzymatic pre-treatment promoted a reduction in methane production, suggesting the possibility of P. ostreatus producing secondary metabolites that can act as inhibitors of the anaerobic consortium, as well as non-inhibitory concentrations of phenolic compounds may be important for the microbial consortium in anaerobic digestion. (AU)

• FAPESP's process: 21/15144-4 - Basidiomycete in the pretreatment of anaerobic digestion of coffee processing wastewater
• Grantee: Fabricio Soares Moreira
• Support Opportunities: Scholarships in Brazil - Master