Full text
| |
| Author(s): |
Andressa Gomes Barroso
Total Authors: 1
|
| Document type: | Master's Dissertation |
| Press: | São Carlos. |
| Institution: | Universidade de São Paulo (USP). Escola de Engenharia de São Carlos (EESC/SBD) |
| Defense date: | 2025-02-20 |
| Examining board members: |
Guilherme Henrique Duarte de Oliveira;
Rachel Biancalana Costa;
Jose Geraldo da Cruz Pradella
|
| Advisor: | Guilherme Henrique Duarte de Oliveira |
| Abstract | |
Polyhydroxyalkanoates (PHA) are fully biodegradable polyesters that can be produced from agro-industrial waste. Soy molasses appear to be a viable byproduct for biopolymer production due to its high carbohydrate content, which can be easily converted into organic acids. PHA is internally synthesized by certain microorganisms that can be selected from mixed microbial cultures (MMC) under alternating substrate availability conditions, known as feast-famine (FF) cycles. The biological production of PHA by MMC typically involves a three-stage process: (i) acidogenic fermentation; (ii) microbial enrichment and selection; and (iii) PHA accumulation. This study aimed to investigate the enrichment of a PHA-producing MMC in a sequencing batch reactor fed with acidified soy molasses and subjected to a gradual increase in the applied organic load rate (OLR) (2.0, 3.5, and 7.0 kg COD m-3 d-1). The acidified effluent was used for MMC enrichment and PHA production, achieving a maximum volumetric productivity of 0.15 g PHA L-1 h-1 and a yield of 0.03 g CODPHA g CODdosed-1 for enrichment performed at a OLR of 6.78 ± 0.37 kg COD m-3 d-1. Accumulation experiments using acidified soy molasses fortified with organic acids (79.0 g COD L-1) led to a maximum volumetric productivity of 0.38 g PHA L-1 h-1 and a yield of 0.48 g CODPHA g CODdosed-1. The evaluation of OLR effects revealed that the most suitable load for MMC selection was applied in Stage 3 (7.0 kg COD m-3 d-1), based on the specific PHA production rate (0.35 mg CODPHA mg CDM-1 h-1), the average F/M ratio during the analyzed period (0.13 ± 0.04), and the resulting accumulation with fortified molasses. The PHA produced was a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) copolymer. The mass ratio of HB:HV in the produced PHA ranged from 82:18 to 88:12 (HB:HV) in experiments without fortified substrate, while in experiments with fortified substrate, the composition shifted to 65:35 (HB:HV). (AU) | |
| FAPESP's process: | 23/05911-3 - SOY MOLASSES AS A SUBSTRATE FOR THE PRODUCTION OF POLYHYDROXYALKANOATES (PHA) BY MIXED MICROBIAL CULTURES: Effects of the Applied Organic Load |
| Grantee: | Andressa Gomes Barroso |
| Support Opportunities: | Scholarships in Brazil - Master |