Héctor A. Ruiz

Effect of chitosan-based coatings on the shelf life of Salmon (Salmo salar)

This study aimed at determining the effect of chitosan coating on shelf life extension of salmon ( Salmo salar ) fillets. The success of edible coatings depends highly on their effective wetting capacity of the surfaces on which they are applied. In this context in a first stage the surface properties of salmon fillets and the wetting capacity of the coatings on fish were evaluated. In terms of wettability there were no significant differences (p > 0.05) between the solutions presenting higher values (solutions 1-4); therefore, solution 1 with a spreading coefficient (Ws) of -4.73 mN m(-1), was chosen to be subsequently analyzed and applied on fish fillets. For shelf life analyses the fillets were coated and stored at 0 °C for 18 days. The control and coated fish samples were analyzed periodically for total aerobic plate count (TPC), pH, total volatile base nitrogen (TVB-N), trimethylamine (TMA), thiobarbituric acid (TBA), and ATP breakdown products (K value). The results showed that fish samples coated with chitosan presented a significant reduction (p < 0.05) for pH and K value after 6 days and for TVB, TMA, and TBA values after 9 days of storage, when compared to control samples. In terms of microbial growth, a slower increase in TPC was observed for the coated fish, indicating that chitosan-based coatings were effective in extending for an additional 3 days the shelf life of the salmon. These results demonstrate that chitosan-based coatings may be an alternative for extending the shelf life of salmon fillets during storage at 0 °C.

Biorefinery valorization of autohydrolysis wheat straw hemicellulose to be applied in a polymer-blend film

The aims of this study were the extraction of hemicellulose from wheat straw (WS) and its utilization in the reinforcement of a κ-carrageenan/locust bean gum (κ-car/LBG) polymeric blend films (PBFs). WS hemicellulose extraction was performed under autohydrolysis process and hemicellulose extracted (HE) under optimum condition was used in PBFs. PBFs were prepared varying different proportions of HE into the κ-car/LBG film-forming solutions. Barrier properties (water vapor permeability, WVP), mechanical properties (tensile-strength, TS and elongation-at-break, EB), moisture content, opacity and thermal properties of the resulting PBFs were determined and related with the incorporation of HE. The 2-3-2 proportion (in the high ratio) of PBF (κ-car/LBG/HE) causes a slight decrease of WVP and an increase of the TS, thus resulting in an improvement of the physical properties of PBFs. HE showed to be a promising material in order to reinforce κ-car/LBG PBF and can be an alternative in the application of hemicellulose according to biorefinery concept.

Industrial robust yeast isolates with great potential for fermentation of lignocellulosic biomass.

The search of robust microorganisms is essential to design sustainable processes of second generation bioethanol. Yeast strains isolated from industrial environments are generally recognised to present an increased stress tolerance but no specific information is available on their tolerance towards inhibitors that come from the pretreatment of lignocellulosic materials. In this work, a strategy for the selection of different yeasts using hydrothermal hydrolysate from Eucalyptus globulus wood, containing different concentrations of inhibitors, was developed. Ten Saccharomyces cerevisiae and four Kluyveromyces marxianus strains isolated from industrial environments and four laboratory background strains were evaluated. Interestingly, a correlation between final ethanol titer and percentage of furfural detoxification was observed. The results presented here highlight industrial distillery environments as a remarkable source of efficient yeast strains for lignocellulosic fermentation processes. Selected strains were able to resourcefully degrade furfural and HMF inhibitors, producing 0.8g ethanol/Lh corresponding to 94% of the theoretical yield.

Evaluation of agave bagasse recalcitrance using AFEX™, autohydrolysis, and ionic liquid pretreatments

A comparative analysis of the response of agave bagasse (AGB) to pretreatment by ammonia fiber expansion (AFEX™), autohydrolysis (AH) and ionic liquid (IL) was performed using 2D nuclear magnetic resonance (NMR) spectroscopy, wet chemistry, enzymatic saccharification and mass balances. It has been found that AFEX pretreatment preserved all carbohydrates in the biomass, whereas AH removed 62.4% of xylan and IL extracted 25% of lignin into wash streams. Syringyl and guaiacyl lignin ratio of untreated AGB was 4.3, whereas for the pretreated biomass the ratios were 4.2, 5.0 and 4.7 for AFEX, AH and IL, respectively. Using NMR spectra, the intensity of β-aryl ether units in aliphatic, anomeric, and aromatic regions decreased in all three pretreated samples when compared to untreated biomass. Yields of glucose plus xylose in the major hydrolysate stream were 42.5, 39.7 and 26.9kg per 100kg of untreated AGB for AFEX, IL and AH, respectively.

A New Approach on Brewer’s Spent Grains Treatment and Potential Use as Lignocellulosic Yeast Cells Carriers

The major objective of this work is to improve the pretreatments of brewers spent grains (BSG) aiming at their use as a source for lignocellulosic yeast carriers (LCYC) production. Therefore, several pretreatments of BSG have been designed aiming at obtaining various yeast carriers, differing on their physicochemical composition. Cellulose, hemicellulose, lignin, fat, protein, and ash content were determined for crude BSG and the LCYCs. The long chain fatty acids profile for the crude BSG was also analyzed. Chemical treatments successfully produced several different LCYC based on BSG. The highest cellulose content in LCYC was achieved upon application of caustic (NaOH) treatment during 40 min. Either caustic or combined acid-caustic treatments predominately generated hydrophobic, negatively charged LCYC. The feasibility of using BSG for LCYC production is strengthened by the fact that added-value byproduct can be extracted before the chemical treatments are applied.

Bioenergy Potential, Energy Crops, and Biofuel Production in Mexico

The negative impact of burning fossil fuels on the global climate, uncertainty over the long-term price of fossil fuels— caused in part by geopolitics and pending decisions on the exploration of oil shale and gas, tar sands and arctic oil reserves, and in part by uncertainty over future regulations on greenhouse gas emissions—and the increasing global demand for energy resulting from population growth and economic development drive the need to deploy renewable energy on a large scale. Mexico is a promising country in the development of renewable energy due to its warm and sunny climate, which supports solar energy generation and crop cultivation throughout the year, and its relative abundance of agricultural land that is suitable for energy crops, but not for food crops, thus minimizing competition between food and energy production. With a well developed infrastructure of roads, ports, and industrial centers, and a relatively low cost of labor, Mexico is among the most relevant emerging bioeconomies. In a recent study, Alemán-Nava et al. [1] reported the current use and future potential of renewable sources in the production of renewable energy, which included solar, hydroelectric, geothermal and wind energy, and bioenergy. However, these alternative sources of energy have not yet been fully exploited in Mexico. According to the Mexican Ministry of Energy (SENER) and the National Energy Balance databases [2], in 2014, Mexico produced 8826 PetaJoule (PJ = 10 J) of energy from the following sources: fossil fuels 91.31% (crude oil 63.42%, natural gas 23.56%, coal 3.44%, and condensates from natural gas production 0.89%), nuclear energy 1.14%, and renewables 7.56% (hydroelectric 1.59%, geothermal 1.47%, solar 0.10%, wind 0.26%, biomass 4.12%, and biogas 0.02%); these statistics indicate that fossil fuels still dominate, and that biomass represents only a small proportion of the total. While there are multiple renewable alternatives for the generation of electricity, biofuels are currently the only alternative source of liquid transportation fuels, and while the market share of electric cars is expected to increase, airplanes and ships will continue to require liquid fuels. Biomass is among the most promising feedstocks for the production of biofuels in Mexico, since the net emissions of CO2 are substantially lower compared to the use of both fossil and first-generation biofuels, there is an abundance of biomass, and large-scale biomass production and processing has potential to generate opportunities in different commercial sectors and can contribute to sustainable regional economic development [3, 4]. Furthermore, in recent years, Mexico has made significant changes in public policies to enhance its development of renewable energies. For example, in 2005, the Law on the * Héctor A. Ruiz hector_ruiz_leza@uadec.edu.mx

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.

Hydrothermal Pretreatments of Macroalgal Biomass for Biorefineries

Recently, macroalgal biomass is gaining wide attention as an alternative in the production of biofuels (as bioetanol and biogas) and compounds with high added value with specific properties (antioxidants, anticoagulants, anti-inflammatories) for applications in food, medical and energy industries in accordance with the integrated biorefineries. Furthermore, biorefinery concept requires processes that allow efficient utilization of all components of the biomass. The pretreatment step in a biorefinery is often based on hydrothermal principles of high temperatures in aqueous solution. Therefore, in this chapter, a review on the application of hydrothermal pretreatment on macroalgal biomass is presented.

Multi-step approach to add value to corncob: production of biomass-degrading enzymes, lignin and fermentable sugars.

This work presents an integrated and multi-step approach for the recovery and/or application of the lignocellulosic fractions from corncob in the production of high value added compounds as xylo-oligosaccharides, enzymes, fermentable sugars, and lignin in terms of biorefinery concept. For that, liquid hot water followed by enzymatic hydrolysis were used. Liquid hot water was performed using different residence times (10-50min) and holding temperature (180-200°C), corresponding to severities (log(R0)) of 3.36-4.64. The most severe conditions showed higher xylo-oligosaccharides extraction (maximum of 93%) into the hydrolysates and higher recovery of cellulose on pretreated solids (maximum of 65%). Subsequently, hydrolysates and solids were used in the production of xylanases and cellulases, respectively, as well as, pretreated solids were also subjected to enzymatic hydrolysis for the recovery of lignin and fermentable sugars from cellulose. Maximum glucose yield (100%) was achieved for solids pretreated at log(R0) of 4.42 and 5% solid loading.

Rhizopus oryzae – Ancient microbial resource with importance in modern food industry

Filamentous fungi are microorganisms widely known for their diverse biochemical features. Fungi can efficiently invade a wide variety of substrates under operational conditions producing numerous bioproducts of interest, such as enzymes, organic acids, aromatic compounds and colorants. An additional interesting characteristic of some fungi is their safety classification for different uses, which guarantees that the bioproducts obtained from them do not contain any toxic component deleterious to humans. Rhizopus oryzae is among this group of fungi and is classified as a GRAS filamentous fungus, commonly used for production of some oriental traditional foods. It is mainly recognized as a good producer of lactic acid; however, its potential for other biotechnological processes is under study. This review analyzes and discusses the current scientific and technical contributions which may maximize the potential of R. oryzae as a producer of different compounds of industrial interest.