Full text
| |
| Author(s): |
Guilherme Soares Cavalcante
Total Authors: 1
|
| Document type: | Doctoral Thesis |
| Press: | São Carlos. |
| Institution: | Universidade de São Paulo (USP). Escola de Engenharia de São Carlos (EESC/SBD) |
| Defense date: | 2021-10-22 |
| Examining board members: |
Marcelo Zaiat;
Marcio Gomes Barboza;
Simone Damasceno Gomes;
Dagoberto Yukio Okada;
Giovana Tommaso
|
| Advisor: | Marcelo Zaiat |
| Abstract | |
Lactic acid has a wide range of applications, one of such is the production of polylactic acid (PLA). PLA is a thermoplastic, biocompatible and biodegradable polymer with good mechanical properties, with potential to compete with other polymer made of petrochemical sources. Utilization of refined sugars by pure microorganisms in sterile media are the most important drawbacks in lactic acid production. Cassava wastewater has the potential to be a suitable substrate for lactic acid production, due to its high carbohydrates content and presence of lactic acid bacteria (LAB). The objective of this study was to assess the feasibility of lactic acid production using cassava wastewater and autochthonous microorganisms in anaerobic reactors. Three experimental phases were performed. In the first phase, a preliminary batch test was conduct to identify the products generated during the fermentation of raw cassava wastewater. Influence of temperature was also investigated. In the second phase, response surface methodology (RSM) was utilized to obtain the best temperature and initial pH conditions for lactic acid production. The kinetics of the process was modelled to assist with the sizing of the continuous reactor. On the third phase, a Anaerobic Bioreactor with Fixed-Structured Bed (ABFSB) was operated to assess the continuous production of lactic acid using raw cassava wastewater in three different hydraulic retention time (HRT) conditions. Results show that the fermentation of cassava wastewater mainly results in lactic acid, ethanol and acetic acid. Lactic acid Selectivity (SAL) was influenced by the different temperatures in phase 1. Results from the RSM indicate that 35 ºC and initial pH of 4.5 was the best condition for lactic acid yield (YAL), resulting in values of 200 mmol.L-1, 0.9 and 0.9 for maximum lactic acid concentration, SAL and YAL, respectively. Continuous lactic acid production was maintained during all ABFSB operation. CCha values above 4 g Ch.L-1.day-1 did not result in significant change in the QAL, with value of 60 g AL.day-1. TDH drop to 8 h, with CCha values between 4 and 7 g Ch.L-1.day-1, resulted in the production of propionic acid, which reduced SAL and YAL. It was estimated that each ton of processed cassava roots has the potential do produce 6 kg of LA. These results show that cassava wastewater has a great potential of lactic acid production using autochthonous microorganisms. (AU) | |
| FAPESP's process: | 16/03470-6 - Lactic acid production from puba production wastewater in fixed bed reactors |
| Grantee: | Jéssica Soares Cavalcante |
| Support Opportunities: | Scholarships in Brazil - Doctorate (Direct) |