Rosa M. Rodríguez-Jasso

Comparison of microwave and conduction-convection heating autohydrolysis pretreatment for bioethanol production

This work describes the application of two forms of heating for autohydrolysis pretreatment on isothermal regimen: conduction-convection heating and microwave heating processing using corn stover as raw material for bioethanol production. Pretreatments were performed using different operational conditions: residence time (10-50 min) and temperature (160-200°C) for both pretreatments. Subsequently, the susceptibility of pretreated solids was studied using low enzyme loads, and high substrate loads. The highest conversion was 95.1% for microwave pretreated solids. Also solids pretreated by microwave heating processing showed better ethanol conversion in simultaneous saccharification and fermentation process (92% corresponding to 33.8g/L). Therefore, microwave heating processing is a promising technology in the pretreatment of lignocellulosic materials.

Operational Strategies for Enzymatic Hydrolysis in a Biorefinery

The [second generation (2G)] biorefinery is gaining wide attention for the production of biofuels such as bioethanol and coproducts such as xylooligosaccharides using lignocellulosic materials as feedstock. However, enzymatic hydrolysis of pretreated lignocellulosic materials to produce fermentable sugars is a complex-step bioethanol production process. In addition, a bottleneck in lignocellulosic biomass conversion to bioethanol is the cost of these enzymes. Thus, one of the most important objectives and challenges in the production of 2G bioethanol is the development of cost-effective processes at large scale. This chapter gives an overview of enzymatic hydrolysis process, the effect of pretreatment on enzymatic hydrolysis, operational strategies, and reactor design and operation as well as the advances achieved in recent years.

Kinetic Modeling, Operational Conditions, and Biorefinery Products from Hemicellulose: Depolymerization and Solubilization During Hydrothermal Processing

Hydrothermal processing is an interesting technology for the conversion of lignocellulosic biomass in biofuels and compounds in terms of a biorefinery. This process is based on the selective solubilization and depolymerization of hemicellulose fraction (xylan), producing a liquid phase of hemicellulose rich in oligomers (xylooligosaccharides), monosaccharides (mainly xylose), and degradation compounds (furfural and formic acid). Therefore, this chapter presents an overview of mathematical modeling based on pseudo-first-order kinetics and the operating conditions as temperature and time (“severity factor”) during the hydrothermal processing in order to predict the conversion and the produced compounds with high value-added in terms of biorefinery.

Fructosyltransferase Sources, Production, and Applications for Prebiotics Production

Fructooligosaccharides (FOS) are considered prebiotic compounds and are found in different vegetables and fruits but at low concentrations. FOS are produced by enzymat‐ ic transformation of sucrose using fructosyltransferase (FTase). Development of new production methods and search for FTase with high activity and stability for FOS production Is an actual research topic. In this article is discussed the most recent advances on FTase and its applications. Different microorganisms have been tested under various fermentation systems in order to identify and characterize new genes codifying for FTase. Some of these genes have been isolated from bacteria, fungi, and plants, with a wide range of percentages of identity but retaining the eight highly conserved motifs of the hydrolase family 32 glycoside. Therefore, this article presents an overview of the most recent advances on FTase and its applications.

Utilization of Citrus Waste Biomass for Antioxidant Production by Solid-State Fermentation

Citrus fruits such as lemon, orange, grapefruit, and tangerine are consumed for their flavor, low cost, and human health benefits. However, citrus juice extraction generates by-products that are mostly unused and is discharged in landfills. In this study, the by-products of lemon, orange, grapefruit, and tangerine were subjected to solid-state fermentation (SSF) using Fusarium oxysporum, Penicillium purpurogenum GH2, Trichoderma harzianum T1-04, and Aspergillus niger GH1 to enhance their antioxidant activity. After fermentation, ethanol extracts were obtained and tested for their antioxidative activity by employing three techniques, 2,2-diphenyl-1-picrylhydrazyl (DPPH˙), ferric reducing antioxidant power (FRAP), and lipid oxidation inhibition (LOI). An increase in antioxidant activity from 33.13 to 41.62 mg/gmsi of antioxidants after fermentation of tangerine by-products by A. niger GH1 was observed. Major compounds present in ethanol extracts obtained after fermentation by A. niger GH1were identified by HPLC-MS, and their m/z corresponded to chlorogenic acid, didymin, naringin, and hesperidin. These results indicated that SSF is a suitable method to enhance antioxidant activity of citrus by-products.

Hydrothermal Processes for Extraction of Macroalgae High Value-Added Compounds

Macroalgae are a complex biomass conformed of unique compounds with high value-added potential for applications in diverse areas such as pharmaceutical, medical, food, material, and biofuel. The pretreatment conditions for macroalgae fractionation into target molecules are essential to remain relevant biological and chemical properties including antiviral, anti-inflammatory, antiangiogenic, antiproliferative, antitumoral, anticoagulant, antioxidant, and gelation activities. Therefore, green technologies such as hydrothermal processes using different heating sources as microwaves, conduction-convection under high-pressure systems, and steam explosion have been recently studied to evaluate the efficiency of this process taking into account the effect over the environment and the economic viability. The present overview describes and discusses the most recent and relevant studies based on hydrothermal processes over the extraction of high value-added and bioactive compounds from macroalgae sources.

Bioeconomy and Biorefinery: Valorization of Hemicellulose from Lignocellulosic Biomass and Potential Use of Avocado Residues as a Promising Resource of Bioproducts

Biorefineries of second generation (2G) are receiving more attention nowadays as an option for the development of bioeconomy all over the world. One of the main pretreatments utilized in this type of facilities for the conversion of lignocellulosic biomass is the use of hydrothermal processing using only water/steam as catalyst under different forms of heating (steam, electric heating jackets, or microwave radiation) at different temperatures. Currently, biorefineries are focused on obtaining feedstocks to produce biofuels, but the current position of these on the market shows that the new biorefineries must be integrated systems and so there is a need to focus on the valorization of the whole coproducts. One of them is hemicellulose, from which for instance oligomers could be derived and used in different areas as pharmaceutical products, food ingredients, fuels, chemicals, and bioplastics. In Mexico, avocado represents an important source for agro-industrial residues. These residues are in a process of valorization under the biorefinery concept, to obtain different types of bioproducts. This chapter describes the concepts usually utilized for the definition and understanding of biorefinery, especially the utilization of hydrothermal pretreatments. It focuses also on linking the concept of bioeconomy with biorefineries, and it introduces the utilization of avocado residues as an example of a Mexican residue with potential importance in the global market.

3 – Pectinolytic Enzymes

Pectinase is an important enzyme that finds application in many food-processing industries. The microbial pectinases represent a large portion of the global food enzymes sales, and the majority of them are from fungal sources. The production of pectinase is done industrially and thus can be considered a consolidated bioprocess. This chapter is focused on providing updated information on a consolidated bioprocess for pectic substances, pectinase classification, pectinase assays, pectinase production processes (raw materials, carbon sources, microorganisms, systems of production by solid-state and submerged fermentation, types of bioreactors), downstream processes, purification methods, and technoeconomic analysis of pectinase production.