Toward the use of mixed microbial cultures for the biological production of adipic and levulinic acid

This research was funded by Fondecyt Postdoctorado No. 3210626, Agencia Nacional de Investigación y Desarrollo de Chile, ANID.The Supplementary material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fmicb.2023.1224543/ full#supplementary-materialBiological synthesis of high added-value compounds like adipic acid (AA), levulinic acid (LA), or polyhydroxybutyrate (PHB) using pure culture has been separately reported. However, pure culture requires sterile conditions and the use of specific carbon sources resulting in high operating costs. Different alternatives based on the use of mixed microbial cultures (MMC) have been explored to resolve this problem. MMC have been widely reported for the production of PHB, but scarcely reported for LA production and never for AA synthesis. This work presents a novel strategy for the co-production of AA LA, and PHB using MMC. The strategy consists in selecting an MMC producer of AA, LA and PHB from an inoculum obtained from a wastewater treatment plant, which is then subjected to the feast and famine culture strategy in a sequential batch reactor, coupled with a batch reactor step to enhance the accumulation of AA and LA. The results showed that the MMC could produce a 16 & PLUSMN; 2, 23 & PLUSMN; 1 and 5 & PLUSMN; %1 (g compound/g volatile solids) of AA, LA and PHB, respectively, using a non-fermented residual biomass rich in pentose, namely synthetic hemicellulose hydrolysate (SHH) as the carbon source. These results contribute to generating future research to better understand and optimise the biosynthesis of these compounds by MMC.Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) CONICYT FONDECYT 3210626Agencia Nacional de Investigacion y Desarrollo de Chile, ANIDUniversities Department of the Andalucia Autonomous Government for his Emergia fellowship (EMERGIA20_00114

Toward the use of mixed microbial cultures for the biological production of adipic and levulinic acid

Biological synthesis of high added-value compounds like adipic acid (AA), levulinic acid (LA), or polyhydroxybutyrate (PHB) using pure culture has been separately reported. However, pure culture requires sterile conditions and the use of specific carbon sources resulting in high operating costs. Different alternatives based on the use of mixed microbial cultures (MMC) have been explored to resolve this problem. MMC have been widely reported for the production of PHB, but scarcely reported for LA production and never for AA synthesis. This work presents a novel strategy for the co-production of AA LA, and PHB using MMC. The strategy consists in selecting an MMC producer of AA, LA and PHB from an inoculum obtained from a wastewater treatment plant, which is then subjected to the feast and famine culture strategy in a sequential batch reactor, coupled with a batch reactor step to enhance the accumulation of AA and LA. The results showed that the MMC could produce a 16 ± 2, 23 ± 1 and 5 ± %1 (g compound/g volatile solids) of AA, LA and PHB, respectively, using a non-fermented residual biomass rich in pentose, namely synthetic hemicellulose hydrolysate (SHH) as the carbon source. These results contribute to generating future research to better understand and optimise the biosynthesis of these compounds by MMC.Fil: Pinto Ibieta, Fernanda. Universidad Católica de Temuco; ChileFil: Cea, Mara. Universidad de La Frontera; ChileFil: Serrano, Antonio. Universidad de Granada; EspañaFil: Felissia, Fernando Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Materiales de Misiones. Universidad Nacional de Misiones. Facultad de Ciencias Exactas, Químicas y Naturales. Instituto de Materiales de Misiones; ArgentinaFil: Area, Maria Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Materiales de Misiones. Universidad Nacional de Misiones. Facultad de Ciencias Exactas, Químicas y Naturales. Instituto de Materiales de Misiones; ArgentinaFil: Cabrera, Francisco. Universidad Autónoma de Chile; ChileFil: Ciudad, Gustavo. Universidad de La Frontera; Chil

Use of Anthracophyllum discolor and Stereum hirsutum as a Suitable Strategy for Delignification and Phenolic Removal of Olive Mill Solid Waste

This study evaluated the use of the white-rot fungi (WRF) Anthracophyllum discolor and Stereum hirsutum as a biological pretreatment for olive mill solid mill waste (OMSW). The WRF strains proposed were added directly to OMSW. The assays consisted of determining the need to add supplementary nutrients, an exogenous carbon source or use agitation systems, and evaluating WRF growth, enzyme activity, phenolic compound removal and lignin degradation. The highest ligninolytic enzyme activity was found at day 10, reaching 176.7 U/L of manganese-independent peroxidase (MniP) produced by A. discolor, and the highest phenolic removal (more than 80% with both strains) was reached after 24 days of incubation. The confocal laser scanning microscopy analysis (CLSM) confirmed lignin degradation through the drop in lignin relative fluorescence units (RFU) from 3967 for untreated OMSW to 235 and 221 RFU, showing a lignin relative degradation of 94.1% and 94.4% after 24 days of treatment by A. discolor and S. hirsutum, respectively. The results demonstrate for the first time that A. discolor and S. hirsutum were able to degrade lignin and remove phenolic compounds from OMSW using this as the sole substrate without adding other nutrients or using agitation systems. This work indicates that it could be possible to design an in situ pretreatment of the valorization of OMSW, avoiding complex systems or transportation. In this sense, future research under non-sterile conditions is needed to evaluate the competition of WRF with other microorganisms present in the OMSW. The main drawbacks of this work are associated with both the low reaction time and the water addition. However, OMSW is seasonal waste produced in one season per year, being stored for a long time. In terms of water addition, the necessary optimization will be addressed in future research

Acid Hydrothermal Amendment of Grape Wine Pomace: Enhancement of Phenol and Carbohydrate Co-Solubilization

Byproducts from the winery industry contain many bioactive compounds that are considered high-value-added compounds. White grape pomace (GP) is rich in carbohydrates; consequently, it can be used as a raw material for subsequent bioprocesses. In the present study, low-temperature hydrothermal treatments were carried out using different operational conditions regarding temperature (65–95 °C), time (120–240 min), and sulfuric acid addition at various concentrations (5–15% v/v). The results showed that by using a temperature of 65 °C, a period of 120 min, and 15% (v/v) of H2SO4, it was possible to obtain a liquid phase rich in phenols and carbohydrates, with total phenol compounds corresponding to 2113 ± 140 mg of gallic acid/kg GP and composed mainly of 3-hydroxytyrosol (1330 ± 22 mg/kg GP). In parallel, carbohydrate solubilization reached 245 g glucose/kg GP. These results demonstrate the promising potential of hydrothermally treated grape pomace as raw material for biorefinery processes

Strategy for biological co-production of levulinic acid and polyhydroxyalkanoates by using mixed microbial cultures fed with synthetic hemicellulose hydrolysate

Hemicellulose hydrolysates (HH), which could be an interesting carbon source to feed mixed microbial cultures (MMC) able to accumulate high value-added compounds. This research focused on the evaluation of a culture strategy to achieve the simultaneous biological production of Levulinic Acid (LA) and Polyhydroxyalcanoates (PHA) by MMC fed with a synthetic HH (SHH). The culture strategy involves the use of sequential batch reactors (SBR) to select microorganisms capable of producing LA and PHA. This work proved that the cultivation strategy used allowed the biological production of LA, reaching 37%w/w when the SHH was composed of 85% pentoses. In addition, the simultaneous biological production of LA and PHB was possible when the SHH was enriched with acetate (45% pentoses - 50% acetate). Finally, this study showed that the composition of the SHH impacts directly on the selected microorganism genus and the type and quantity of the value-added compounds obtained.Fil: Pinto Ibieta, Fernanda. Universidad de La Frontera; Chile. Universidad Catolica de Temuco; ChileFil: Cea, Mara. Universidad de la Frontera. Facultad de Ingeniería y Ciencias; ChileFil: Cabrera, Francisco. Universidad Autónoma de Chile; ChileFil: Abanto, Michel. Universidad de La Frontera; ChileFil: Felissia, Fernando Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Materiales de Misiones. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Instituto de Materiales de Misiones; ArgentinaFil: Area, Maria Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Materiales de Misiones. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Instituto de Materiales de Misiones; ArgentinaFil: Ciudad, Gustavo. Universidad de La Frontera; Chil