María López-Abelairas

Fungal pretreatment: An alternative in second-generation ethanol from wheat straw

The potential of a fungal pretreatment combined with a mild alkali treatment to replace or complement current physico-chemical methods for ethanol production from wheat straw has been investigated. Changes in substrate composition, secretion of ligninolytic enzymes, enzymatic hydrolysis efficiency and ethanol yield after 7, 14 and 21 days of solid-state fermentation were evaluated. Most fungi degraded lignin with variable selectivity degrees, although only eight of them improved sugar recovery compared to untreated samples. Glucose yield after 21 days of pretreatment with Poria subvermispora and Irpex lacteus reached 69% and 66% of cellulose available in the wheat straw, respectively, with an ethanol yield of 62% in both cases. Conversions from glucose to ethanol reached around 90%, showing that no inhibitors were generated during this pretreatment. No close correlations were found between ligninolytic enzymes production and sugar yields.

Alkali treatment of fungal pretreated wheat straw for bioethanol production

Abstract Bioconversion of lignocellulosic materials into ethanol requires an intermediate pretreatment step for conditioning biomass. Sugar yields from wheat straw were previously improved by the addition of a mild alkali pretreatment step before bioconversion by the white-rot fungus Irpex lacteus. In this work, an alternative alkaline treatment, which significantly reduces water consumption, was implemented and optimized. Sugar recovery increased 117% with respect to the previously developed alkaline wash process at optimal process conditions (30°C, 30 minutes and 35.7% (w/w) of NaOH). In order to further reduce operational costs, a system for alkali recycling was implemented. This resulted in the treatment of 150% more wheat straw using the same amount of NaOH. Finally, enzymatic hydrolysis was optimized and resulted in a reduction of enzyme dose of 33%.

Application of flow cytometry for monitoring the production of poly(3‐hydroxybutyrate) by Halomonas boliviensis

In this study, a flow cytometry (FC) protocol was implemented to measure poly(3‐hydroxybutyrate) (PHB) content in a halophilic bacterium, to have a faster and easier control of the process. The halophilic bacterium Halomonas boliviensis was stained with BODIPY 493/503 and analyzed using FC. Bacterial polymer accumulation induced by two different nutrient limitations during the operation of a 2 L bioreactor was studied using traditional gas chromatography (GC) analysis and FC. The application of this rapid and straightforward method is useful to obtain complex and precise information about PHB accumulation that could be used for the monitoring, control and optimization of the production of PHB. A clear correlation between the PHB concentration determined by GC and the fluorescence signal obtained from stained bacteria by using FC was observed. Additionally, the heterogeneity of bacterial population as a function of PHB content was measured.

Application of Fungal Pretreatment in the Production of Ethanol From Crop Residues

Abstract The fungal pretreatment of lignocellulosic biomass for the production of ethanol is a low-cost, safe, and environmentally friendly process that can be used as an alternative to the more energy-demanding physicochemical pretreatments. It is based on the special features of white-rot fungi (WRF), which have the ability to degrade lignin by using extracellular ligninolytic enzymes. Fungal pretreatment has the advantage of selectively removing lignin and increase the digestibility of cellulose and hemicellulose at mild operational conditions, without producing inhibitors. Fungal pretreatment has been applied to different crop residues for producing ethanol, demonstrating that it is capable of handling feedstocks of variable origin. However, the integration of the fungal pretreatment in a biorefinery needs to be adapted to the special characteristics of WRF, to take full advantage of its great potential and to overcome the inherent drawbacks