Lignocellulosic residues as supports for enzyme immobilization, and biocatalysts with potential applications.

Growing demand for agricultural production means a higher quantity of residues produced. The reuse and recycling of agro-industrial wastes reduce worldwide greenhouse emissions. New opportunities are derived from this kind of residuals in the biotechnological field generating valuable products in growing sectors such as transportation, bioenergy, food, and feedstock. The use of natural macromolecules towards biocatalysts offers numerous advantages over free enzymes and friendliness with the environment. Enzyme immobilization improves enzyme properties (stability and reusability), and three types of supports are discussed: inorganic, organic, and hybrid. Several examples of agro-industrial wastes such as coconut wastes, rice husks, corn residues and brewers spent grains (BSG), their properties and potential as supports for enzyme immobilization are described in this work. Before the immobilization, biological and non-biological pretreatments could be performed to enhance the waste potential as a carrier. Additionally, immobilization methods such as covalent binding, adsorption, cross-linking and entrapment are compared to provide high efficiency. Enzymes and biocatalysts for industrial applications offer advantages over traditional chemical processes with respect to sustainability and process efficiency in food, energy, and bioremediation fields. The wastes reviewed in this work demonstrated a high affinity for lipases and laccases and might be used in biodiesel production and textile wastewater treatment, among other applications.

Evaluation of bioremediation strategies for treating recalcitrant halo-organic pollutants in soil environments.

The aim of this study was to investigate the bioremediation potential of polychlorinated biphenyls (PCBs) in soil, mimicking three strategies: (a) mycoaugmentation: by the addition of Trametes sanguinea and Pleurotus sajor-caju co-cultures immobilized on sugarcane bagasse; (b) biostimulation: by supplementation of sugarcane bagasse; and (c) natural attenuation: no amendments. The experiments were done in microcosms using Ultisol soil. Remediation effectiveness was assessed based on pollutants content, soil characteristics, and ecotoxicological tests. Biostimulation and mycoaugmentation demonstrated the highest PCBs-removal (approx. 90%) with a significant toxicity reduction at 90 d. The studied strains were able to survive during the incubation period in non-sterilized soil. Laccase, manganese-peroxidase and endoxylanase activities increased significantly in co-cultures after 60 d. Sugarcane bagasse demonstrated to be not only a suitable support for fungal immobilization but also an efficient substrate for fungal colonization of PCBs-contaminated soils. Mycoaugmentation and biostimulation with sugarcane bagasse improved oxidable organic matter and phosphorous contents as well as dehydrogenase activity in soil. Therefore, biostimulation with sugarcane bagasse and mycoaugmentation applying dual white-rot fungal cultures constitute two efficient bioremediation alternatives to restore PCBs-contaminated soils.

Assessing the ability of white-rot fungi to tolerate polychlorinated biphenyls using predictive mycology.

The aim of the present study was to assess the ability of different white-rot fungi to tolerate polychlorinated biphenyls (PCBs) using predictive mycology, by relating fungal growth inhibition to ligninolityc enzyme secretion. Fungal strains were grown in the presence of PCBs in solid media and their radial growth values were modelled through the Dantigny-logistic like function in order to estimate the time required by the fungal colonies to attain half their maximum diameter. The principal component analysis (PCA) revealed an inverse correlation between strain tolerance to PCBs and the laccase secretion over time, being laccase production closely associated with fungal growth capacity. Finally, a PCA was run to regroup and split between resistant and sensitive fungi. Simultaneously, a function associated with a model predicting the tolerance to PCBs was developed. Some of the assayed isolates showed a promising capacity to be applied in PCB bioremediation. Abbreviations: Polychlorinated biphenyls (PCBs), white-rot fungi (WRF).