Effective one-step saccharification of lignocellulosic biomass using magnetite-biocatalysts containing saccharifying enzymes

Advances in L-Lactic Acid Production from Lignocellulose Using Genetically Modified Microbial Systems

Lactic acid is a vital organic acid with a wide range of industrial applications, particularly in the food, pharmaceutical, cosmetic, and biomedical sectors. The conventional production of lactic acid from refined sugars poses high costs and significant environmental impacts, leading to the exploration of alternative raw materials and more sustainable processes. Lignocellulosic biomass, particularly agro-industrial residues such as agave bagasse, represents a promising substrate for lactic acid production. Agave bagasse, a by-product of the tequila and mezcal industries, is rich in fermentable carbohydrates, making it an ideal raw material for biotechnological processes. The use of lactic acid bacteria (LAB), particularly genetically modified microorganisms (GMMs), has been shown to enhance fermentation efficiency and lactic acid yield. This review explores the potential of lignocellulosic biomass as a substrate for microbial fermentation to produce lactic acid and other high-value products. It covers the composition and pretreatment of some agricultural residues, the selection of suitable microorganisms, and the optimization of fermentation conditions. The paper highlights the promising future of agro-industrial residue valorization through biotechnological processes and the sustainable production of lactic acid as an alternative to conventional methods.

Enzyme immobilization technology as a tool to innovate in the production of biofuels: A special review of the Cross-Linked Enzyme Aggregates (CLEAs) strategy

This review emphasizes the crucial role of enzyme immobilization technology in advancing the production of two main biofuels, ethanol and biodiesel, with a specific focus on the Cross-linked Enzyme Aggregates (CLEAs) strategy. This method of immobilization has gained attention due to its simplicity and affordability, as it does not initially require a solid support. CLEAs synthesis protocol includes two steps: enzyme precipitation and cross-linking of aggregates using bifunctional agents. We conducted a thorough search for papers detailing the synthesis of CLEAs utilizing amylases, cellulases, and hemicellulases. These key enzymes are involved in breaking down starch or lignocellulosic materials to produce ethanol, both in first and second-generation processes. CLEAs of lipases were included as these enzymes play a crucial role in the enzymatic process of biodiesel production. However, when dealing with large or diverse substrates such as lignocellulosic materials for ethanol production and oils/fats for biodiesel production, the use of individual enzymes may not be the most efficient method. Instead, a system that utilizes a blend of enzymes may prove to be more effective. To innovate in the production of biofuels (ethanol and biodiesel), enzyme co-immobilization using different enzyme species to produce Combi-CLEAs is a promising trend.

Saccharification of lignocellulosic biomass using an enzymatic cocktail of fungal origin and successive production of butanol by Clostridium acetobutylicum

A multistep approach was undertaken for biobutanol production targeting valorization of agricultural waste. Optimum production of lignocellulolytic enzymes [CMCase (3822.93U/mg), FPase (3640.93U/mg), β-glucosidase (3873.92U/mg), xylanase (3460.24U/mg), pectinase (3359.57U/mg), α-amylase (4136.54U/mg), and laccase (3863.16U/mg)] was accomplished through solid-substrate fermentation of pretreated mixed substrates (wheat bran, sugarcane bagasse and orange peel) by Aspergillus niger SKN1 and Trametes hirsuta SKH1. Partially purified enzyme cocktail was employed for saccharification of the said substrate mixture into fermentable sugar (69.23 g/L, product yield of 24% w/w). The recovered sugar with vegetable extract supplements was found as robust fermentable medium that supported 16.51 g/L biobutanol production by Clostridium acetobutylicum ATCC824. The sequential bioprocessing of low-priced substrates and exploitation of vegetable extract as growth factor for microbial butanol production will open a new vista in biofuel research.

Magnetic Nanomaterials as Biocatalyst Carriers for Biomass Processing: Immobilization Strategies, Reusability, and Applications

Environmental concerns, along with oil shortages, have increased industrial interest in biomass conversion to produce biofuels and other valuable chemicals. A green option in biomass processing is the use of enzymes, such as cellulases, hemicellulases, and ligninolytic (laccase and peroxidases), which have outstanding specificity toward their substrates and can be reused if immobilized onto magnetic nanocarriers. Numerous studies report the biocatalysts’ performance after covalent binding or adsorption on differently functionalized magnetic nanoparticles (MNPs). Functionalization strategies of MNPs include silica-based surfaces obtained through a sol–gel process, graphene oxide-based nanocomposites, polymer-coated surfaces, grafting polymer brushes, and others, which have been emphasized in this review of the immobilization and co-immobilization of enzymes used for biomass conversion. Careful analysis of the parameters affecting the performance of enzyme immobilization for new hybrid matrices has enabled us to achieve wider tolerance to thermal or chemical stress by these biosystems during saccharification. Additionally, it has enabled the application of immobilized laccase to remove toxic organic compounds from lignin, among other recent advances addressed here related to the use of reusable magnetic carriers for bioderived chemical manufacturing.

Nanobiocatalysts for efficacious bioconversion of ionic liquid pretreated sugarcane tops biomass to biofuel

This work aimed to study the hydrolysis of ionic liquid (IL) pretreated sugarcane tops (SCT) biomass with in-house developed IL-stable enzyme preparation, from a fungal isolate Aspergillus flavus PN3. Maximum reducing sugar yield (181.18 mg/g biomass) was obtained from tris (2-hydroxyethyl) methylammonium-methylsulfate ([TMA]MeSO₄) pretreated biomass. Pretreatment parameters were optimized to attain enhanced sugar yield (1.57-fold). Functional mechanism of IL mediated pretreatment of SCT biomass was elucidated by SEM, XRD, FTIR and ¹H NMR studies. Furthermore, nanobiocatalysts prepared by immobilization of enzyme preparation by covalent coupling on magnetic nanoparticles functionalized with amino-propyl triethoxysilane, were assessed for their hydrolytic efficacy and reusability. Nanobiocatalysts were examined by SEM and FTIR analysis for substantiation of immobilization. This is the first ever report of application of magnetic nanobiocatalysts for saccharification of IL-pretreated sugarcane tops biomass.

Bioreactor and Bioprocess Design Issues in Enzymatic Hydrolysis of Lignocellulosic Biomass

Saccharification of lignocellulosic biomass is a fundamental step in the biorefinery of second generation feedstock. The physicochemical and enzymatic processes for the depolymerization of biomass into simple sugars has been achieved through numerous studies in several disciplines. The present review discusses the development of technologies for enzymatic saccharification in industrial processes. The kinetics of cellulolytic enzymes involved in polysaccharide hydrolysis has been discussed as the starting point for the design of the most promising bioreactor configurations. The main process configurations—proposed so far—for biomass saccharification have been analyzed. Attention was paid to bioreactor configurations, operating modes and possible integrations of this operation within the biorefinery. The focus is on minimizing the effects of product inhibition on enzymes, maximizing yields and concentration of sugars in the hydrolysate, and reducing the impact of enzyme cost on the whole process. The last part of the review is focused on an emerging process based on the catalytic action of laccase applied to lignin depolymerization as an alternative to the consolidated physicochemical pretreatments. The laccases-based oxidative process has been discussed in terms of characteristics that can affect the development of a bioreactor unit where laccases or a laccase-mediator system can be used for biomass delignification.

Sugarcane Bagasse Saccharification by Enzymatic Hydrolysis Using Endocellulase and β-glucosidase Immobilized on Different Supports

The saccharification of sugarcane bagasse by enzymatic hydrolysis is one of the most promising processes for obtaining fermentable sugar to be used in the production of second-generation ethanol. The objective of this work was to study the immobilization and stabilization of two commercial enzymes: Endocellulase (E-CELBA) in dextran coated iron oxide magnetic nanoparticles activated with aldehyde groups (DIOMNP) and β-glucosidase (E-BGOSPC) in glyoxyl agarose (GLA) so that their immobilized derivatives could be applied in the saccharification of pretreated sugarcane bagasse. This was the first time that the pretreated sugarcane bagasse was saccharified by cascade reaction using a endocellulase immobilized on dextran coated Fe2O3 with aldehyde groups combined with a β-glucosidase immobilized on glyoxyl agarose. Both enzymes were successfully immobilized (more than 60% after reduction with sodium borohydride) and presented higher thermal stability than free enzymes at 60, 70, and 80 °C. The enzymatic hydrolysis of the sugarcane bagasse was carried out with 15 U of each enzyme per gram of bagasse in a solid-liquid ratio of 1:20 for 48 h at 50 °C. Under these conditions, 39.06 ± 1.18% of the cellulose present in the pretreated bagasse was hydrolyzed, producing 14.11 ± 0.47 g/L of reducing sugars (94.54% glucose). In addition, DIOMNP endo-cellulase derivative maintained 61.40 ± 1.17% of its enzymatic activity after seven reuse cycles, and GLA β-glucosidase derivative maintained up to 58.20 ± 1.55% of its enzymatic activity after nine reuse cycles.

Characterization of Cross-Linked Enzyme Aggregates of the Y509E Mutant of a Glycoside Hydrolase Family 52 β-xylosidase from G. stearothermophilus

Cross-linked enzyme aggregates (CLEAs) of the Y509E mutant of glycoside hydrolase family 52 β-xylosidase from Geobacillus stearothermophilus with dual activity of β-xylosidase and xylanase (XynB2^Y509E) were prepared. Ammonium sulfate was used as the precipitant agent, and glutaraldehyde as cross-linking agent. The optimum conditions were found to be 90% ammonium sulfate, 12.5 mM glutaraldehyde, 3 h of cross-linking reaction at 25 °C, and pH 8.5. Under these (most effective) conditions, XynB2^Y509E-CLEAs retained 92.3% of their original β-xylosidase activity. Biochemical characterization of both crude and immobilized enzymes demonstrated that the maximum pH and temperature after immobilization remained unchanged (pH 6.5 and 65 °C). Moreover, an improvement in pH stability and thermostability was also found after immobilization. Analysis of kinetic parameters shows that the K _m value of XynB2^Y509E-CLEAs obtained was slightly higher than that of free XynB2^Y509E (1.2 versus 0.9 mM). Interestingly, the xylanase activity developed by the mutation was also conserved after the immobilization process.

Low-Cost Cellulase-Hemicellulase Mixture Secreted by Trichoderma harzianum EM0925 with Complete Saccharification Efficacy of Lignocellulose

Fermentable sugars are important intermediate products in the conversion of lignocellulosic biomass to biofuels and other value-added bio-products. The main bottlenecks limiting the production of fermentable sugars from lignocellulosic biomass are the high cost and the low saccharification efficiency of degradation enzymes. Herein, we report the secretome of Trichoderma harzianum EM0925 under induction of lignocellulose. Numerously and quantitatively balanced cellulases and hemicellulases, especially high levels of glycosidases, could be secreted by T. harzianum EM0925. Compared with the commercial enzyme preparations, the T. harzianum EM0925 enzyme cocktail presented significantly higher lignocellulolytic enzyme activities and hydrolysis efficiency against lignocellulosic biomass. Moreover, 100% yields of glucose and xylose were obtained simultaneously from ultrafine grinding and alkali pretreated corn stover. These findings demonstrate a natural cellulases and hemicellulases mixture for complete conversion of biomass polysaccharide, suggesting T. harzianum EM0925 enzymes have great potential for industrial applications.

Fuzzy modeling and parameters optimization for the enhancement of biodiesel production from waste frying oil over montmorillonite clay K-30

Transesterification is a promising technology for the biodiesel production to provide an alternative fuel that considers the environmental concerns. From the economic and environmental protection points of view, utilization of waste frying oil for the production of biodiesel addresses very beneficial impacts. Production of higher yield of biodiesel is a challenging process in order to commercialize it with a lower cost. The current study focuses on the influence of different parameters such as reaction temperature (°C), reaction period (min), oil to methanol ratio and amount of catalyst (wt%) on the production of biodiesel. The main objective of this work is to develop a model via fuzzy logic approach in order to maximize the biodiesel produced from waste frying oil using montmorillonite Clay K-30 as a catalyst. The optimization for the operating parameters has been performed via particle swarm optimization (PSO) approach. During the optimization process, the decision variables were represented by four different operating parameters: temperature (40-140 °C), reaction period (60-300 min), oil/methanol ratio (1:6-1:18) and amount of catalyst (1-5 wt%). The model has been validated with the experimental data and compared with the optimal results reported based on other optimization techniques. Results showed the increment of biodiesel production by 15% using the proposed strategy compared to the earlier study. The obtained biodiesel production yield reached 93.70% with the optimal parameters for a temperature at 69.66 °C, a reaction period of 300 min, oil/methanol ratio of 1:9 and an amount of catalyst of 5 wt%.

CLEAs, Combi-CLEAs and ‘Smart’ Magnetic CLEAs: Biocatalysis in a Bio-Based Economy

Biocatalysis has emerged in the last decade as a pre-eminent technology for enabling the envisaged transition to a more sustainable bio-based economy. For industrial viability it is essential that enzymes can be readily recovered and recycled by immobilization as solid, recyclable catalysts. One method to achieve this is via carrier-free immobilization as cross-linked enzyme aggregates (CLEAs). This methodology proved to be very effective with a broad selection of enzymes, in particular carbohydrate-converting enzymes. Methods for optimizing CLEA preparations by, for example, adding proteic feeders to promote cross-linking, and strategies for making the pores accessible for macromolecular substrates are critically reviewed and compared. Co-immobilization of two or more enzymes in combi-CLEAs enables the cost-effective use of multiple enzymes in biocatalytic cascade processes and the use of “smart” magnetic CLEAs to separate the immobilized enzyme from other solids has raised the CLEA technology to a new level of industrial and environmental relevance. Magnetic-CLEAs of polysaccharide-converting enzymes, for example, are eminently suitable for use in the conversion of first and second generation biomass.