Delignification of sugarcane bagasse using pretreatment strategies for bioethanol production

Sugarcane bagasse derived xylooligosaccharides produced by an arabinofuranosidase/xylobiohydrolase from Bifidobacterium longum in synergism with xylanases

Arabinoxylan is a major hemicellulose in the sugarcane plant cell wall with arabinose decorations that impose steric restrictions on the activity of xylanases against this substrate. Enzymatic removal of the decorations by arabinofuranosidases can allow a more efficient arabinoxylan degradation by xylanases. Here we produced and characterized a recombinant Bifidobacterium longum arabinofuranosidase from glycoside hydrolase family 43 (BlAbf43) and applied it, together with GH10 and GH11 xylanases, to produce xylooligosaccharides (XOS) from wheat arabinoxylan and alkali pretreated sugarcane bagasse. The enzyme synergistically enhanced XOS production by GH10 and GH11 xylanases, being particularly efficient in combination with the latter family of enzymes, with a degree of synergism of 1.7. We also demonstrated that the enzyme is capable of not only removing arabinose decorations from the arabinoxylan and from the non-reducing end of the oligomeric substrates, but also hydrolyzing the xylan backbone yielding mostly xylobiose and xylose in particular cases. Structural studies of BlAbf43 shed light on the molecular basis of the substrate recognition and allowed hypothesizing on the structural reasons of its multifunctionality.

Enhancing biomass conservation and enzymatic hydrolysis of sweet sorghum bagasse by combining pretreatment with ensiling and NaOH

Lignocellulosic pretreatment is an important stage in biomass utilization, which usually requires high input. In this study, a low-cost method using combined ensiling and NaOH was developed for lignocellulosic pretreatment. Sweet sorghum bagasse (SSB) was ensiled for 21 days and then treated with diluted NaOH (0%, 1%, and 2%) for fermentation. The results showed that the application of Lactobacillus plantarum (L) reduced fermentation losses of the silages, mainly low water-soluble carbohydrate (WSC) and ammonia nitrogen loss. Meanwhile, the application of Lactobacillus plantarum and ensiling enzyme (LE) promoted lignocellulosic degradation, as evidenced by low neutral detergent fiber (NDF), acid detergent fiber (ADF), lignin (ADL), and hemicellulosic (HC) contents. The dominant bacterial genera were Lactobacillus, uncultured_bacterium_f_Enterobacteriaceae, and Pantoea after silage, which corresponded to the higher lactic acid and acetic contents and lower pH. The reducing sugar yields of SSB increased after combined pretreatment of silage and NaOH and were further enhanced by the 2% NaOH application, as evidenced by the high reducing sugar yield and microstructure damage, especially in the L-2% NaOH group and the LE-2% NaOH group, in which the reducing sugar yields were 87.99 and 94.45%, respectively, compared with those of the no additive control (CK)-0 NaOH group. Therefore, this study provides an effective method for SSB pretreatment to enhance biomass conservation.

Sugarcane bagasse into value-added products: a review

Strategic valorization of readily available sugarcane bagasse (SB) is very important for waste management and sustainable biorefinery. Conventional SB pretreatment methods are ineffective to meet the requirement for industrial adaptation. Several past studies have highlighted different pretreatment procedures which are lacking environmentally benign characteristics and effective SB bioconversion. This article provides an in-depth review of a variety of environmentally acceptable thermochemical and biological pretreatment techniques for SB. Advancements in the conversion processes such as pyrolysis, liquefaction, gasification, cogeneration, lignin conversion, and cellulose conversion via fermentation processes are critically reviewed for the formation of an extensive array of industrially relevant products such as biofuels, bioelectricity, bioplastics, bio adsorbents, and organic acids. This article would provide comprehensive insights into several crucial aspects of thermochemical and biological conversion processes, including systematic perceptions and scientific developments for value-added products from SB valorization. Moreover, it would lead to determining efficient pretreatment and/or conversion processes for sustainable development of industrial-scale sugarcane-based biorefinery.

Opportunities in the microbial valorization of sugar industrial organic waste to biodegradable smart food packaging materials

Many petroleum-derived plastics, including food packaging materials are non-biodegradable and designed for single-use applications. Annually, around 175 Mt. of plastic enters the land and ocean ecosystems due to mismanagement and lack of techno economically feasible plastic waste recycling technologies. Renewable sourced, biodegradable polymer-based food packaging materials can reduce this environmental pollution. Sugar production from sugarcane or sugar beet generates organic waste streams that contain fermentable substrates, including sugars, acids, and aromatics. Microbial metabolism can be leveraged to funnel those molecules to platform chemicals or biopolymers to generate biodegradable food packaging materials that have active or sensing molecules embedded in biopolymer matrices. The smart package can real-time monitor food quality, assure health safety, and provide economic and environmental benefits. Active packaging materials display functional properties such as antimicrobial, antioxidant, and light or gas barrier. This article provides an overview of potential biodegradable smart/active polymer packages for food applications by valorizing sugar industry-generated organic waste. We highlight the potential microbial pathways and metabolic engineering strategies to biofunnel the waste carbon efficiently into the targeted platform chemicals such as lactic, succinate, muconate, and biopolymers, including polyhydroxyalkanoates, and bacterial cellulose. The obtained platform chemicals can be used to produce biodegradable polymers such as poly (butylene adipate-co-terephthalate) (PBAT) that could replace incumbent polyethylene and polypropylene food packaging materials. When nanomaterials are added, these polymers can be active/smart. The process can remarkably lower the greenhouse gas emission and energy used to produce food-packaging material via sugar industrial waste carbon relative to the petroleum-based production. The proposed green routes enable the valorization of sugar processing organic waste into biodegradable materials and enable the circular economy.

A Review on the Production of C4 Platform Chemicals from Biochemical Conversion of Sugar Crop Processing Products and By-Products

The development and commercialization of sustainable chemicals from agricultural products and by-products is necessary for a circular economy built on renewable natural resources. Among the largest contributors to the final cost of a biomass conversion product is the cost of the initial biomass feedstock, representing a significant challenge in effective biomass utilization. Another major challenge is in identifying the correct products for development, which must be able to satisfy the need for both low-cost, drop-in fossil fuel replacements and novel, high-value fine chemicals (and/or commodity chemicals). Both challenges can be met by utilizing wastes or by-products from biomass processing, which have very limited starting cost, to yield platform chemicals. Specifically, sugar crop processing (e.g., sugarcane, sugar beet) is a mature industry that produces high volumes of by-products with significant potential for valorization. This review focuses specifically on the production of acetoin (3-hydroxybutanone), 2,3-butanediol, and C4 dicarboxylic (succinic, malic, and fumaric) acids with emphasis on biochemical conversion and targeted upgrading of sugar crop products/by-products. These C4 compounds are easily derived from fermentations and can be converted into many different final products, including food, fragrance, and cosmetic additives, as well as sustainable biofuels and other chemicals. State-of-the-art literature pertaining to optimization strategies for microbial conversion of sugar crop byproducts to C4 chemicals (e.g., bagasse, molasses) is reviewed, along with potential routes for upgrading and valorization. Directions and opportunities for future research and industrial biotechnology development are discussed.

Sugarcane bagasse: a biomass sufficiently applied for improving global energy, environment and economic sustainability

Sugarcane (Saccharum officinarum) bagasse (SCB) is a biomass of agricultural waste obtained from sugarcane processing that has been found in abundance globally. Due to its abundance in nature, researchers have been harnessing this biomass for numerous applications such as in energy and environmental sustainability. However, before it could be optimally utilised, it has to be pre-treated using available methods. Different pre-treatment methods were reviewed for SCB, both alkaline and alkali-acid process reveal efficient and successful approaches for obtaining higher glucose production from hydrolysis. Procedures for hydrolysis were evaluated, and results indicate that pre-treated SCB was susceptible to acid and enzymatic hydrolysis as > 80% glucose yield was obtained in both cases. The SCB could achieve a bio-ethanol (a biofuel) yield of > 0.2 g/g at optimal conditions and xylitol (a bio-product) yield at > 0.4 g/g in most cases. Thermochemical processing of SCB also gave excellent biofuel yields. The plethora of products obtained in this regard have been catalogued and elucidated extensively. As found in this study, the SCB could be used in diverse applications such as adsorbent, ion exchange resin, briquettes, ceramics, concrete, cement and polymer composites. Consequently, the SCB is a biomass with great potential to meet global energy demand and encourage environmental sustainability.

Briquetting of sugarcane bagasse as a proper waste management technology in Vietnam

The present research describes an application of high-pressure briquetting technology to the waste management of sugarcane processing in Vietnam. The amount of generated sugarcane bagasse was monitored during sugarcane processing within the street juice production in Hue city, Vietnam. Generated sugarcane bagasse was subjected to fuel parameters analysis within its suitability for direct combustion. The obtained sugarcane bagasse was converted into bio-briquette fuel by a high-pressure briquetting press and its mechanical quality was determined. Results proved that the proportion of generated sugarcane bagasse from whole sugarcane stem mass was equal to 35.45%. This indicated generation of an abundant amount of sugarcane bagasse worldwide in general. Fuel parameters analysis proved high quality level of low ash content = 0.97% and high calorific values (gross calorific value = 18.35 MJ·kg^-1, net calorific value = 17.06 MJ·kg^-1), which indicated good suitability for direct combustion processes. Indicators of mechanical quality proved the following observations: mechanical durability = 99.29%, compressive strength = 150.82 N∙mm^-1 and bulk density = 1022.44 kg·m^-3, with all these indicators representing positive results. In general, the observed results indicated suitability of sugarcane bagasse valorization within the production of bio-briquette fuel by using high-pressure briquetting technology. Finally, analysis of such waste biomass proved its great potential for energy recovery, thus, the advantage of its valorization within the sustainable technologies.

Saccharification Yield through Enzymatic Hydrolysis of the Steam-Exploded Pinewood

Pressure, temperature, and retention time are the most studied parameters in steam explosion pretreatment. However, this work aimed to fix these parameters and to evaluate the influences of several less investigated steam explosion parameters on the saccharification yield in hydrolysis. In this study, firstly, pinewood samples smaller than 200 µm were treated with steam explosion at 190 °C for 10 min. The variable parameters were biomass loading, N2 pressure, and release time. Steam-exploded samples were hydrolyzed with the Trichoderma reesei enzyme for saccharification for 72 h. The sugar content of the resultant products was analyzed to estimate the yield of sugars (such as glucose, xylose, galactose, mannose, and arabinose). The best glucose yield in the pulp was achieved with 4 g of sample, N2 pressure of 0.44 MPa, and short release time (22 s). These conditions gave a glucose yield of 97.72% in the pulp, and the xylose, mannose, galactose, and arabinose yields in the liquid fraction were found to be 85.59%, 87.76%, 86.43%, and 90.3%, respectively.

Selective removal of phosphate from aqueous solution by MIL-101(Fe)/bagasse composite prepared through bagasse size control

MIL-101(Fe)/sugarcane bagasse (SCB) with high adsorption capacity and selectivity toward phosphate was prepared through in-situ synthesis method. Effects of bagasse size on the morphology and performances of the composites were investigated, and adsorption behavior and mechanism of phosphate on the composite prepared at the optimum bagasse size were studied. Results showed that composite prepared with bagasse size of 200-300 mesh (MIL-101(Fe)/SCB₃) showed much higher adsorption capacity than SCB, blank MIL-101(Fe) and the composites prepared with the other bagasse size, which was due to the more positively charged surface and the more exposed adsorption active sites including FeOH_x and exchangeable Cl^-. Co-ions experimental results illustrated that the as prepared MIL-101(Fe)/SCB₃ showed high adsorption affinity toward phosphate, and the common cationic and anionic ions exhibited negligible effects on phosphate adsorption capacity and rate. The optimum pH range for phosphate adsorption on MIL-101(Fe)/SCB₃ was from 3.0 to 10.0, and in this range Fe release was less than 0.03%. Adsorption mechanism showed that phosphate was adsorbed mainly through electrostatic force, ion-exchange, and inner-sphere surface complex. Simulated wastewater treatment experiment showed that MIL-101(Fe)/SCB₃ could efficiently remove phosphate from aqueous solution.

Totally green cellulose conversion into bio-oil and cellulose citrate using molten citric acid in an open system: synthesis, characterization and computational investigation of reaction mechanisms

The simultaneous transformation of crystalline or amorphous cellulose into a furan-based bio-oil and cellulose citrate was realized avoiding the use of strong inorganic acids, drastic conditions, enzymatic treatments or microorganism fermentation. This innovative method is very eco-friendly and involves the use of molten citric acid under solvent free conditions at atmospheric pressure. An accurate discussion on chemical composition of the bio-oil enriched in bioprivileged molecules as well as structural and morphological characterization of cellulose citrate was reported. Moreover, mechanistic hypotheses were formulated on the basis of experimental findings and detailed DFT quantum-mechanical simulations were carried out to confirm, step by step, the proposed reaction paths.

Innovative and efficient conversion of cellulose in furan-based bio-oil and cellulose citrate.