Comparison of industrially viable pretreatments to enhance soybean straw biodegradability

Recent advances and sustainable development of biofuels production from lignocellulosic biomass

Many countries in the world are facing the demand for non-renewable fossil fuels because of overpopulation and economic boom. To reduce environmental pollution and zero carbon emission, the conversion of biomass into biofuels has paid better attention and is considered to be an innovative approach. A diverse raw material has been utilized as feedstock for the production of biofuel, depending on the availability of biomass, cost-effectiveness, and their geographic location. Among the different raw materials, lignocellulosic biomass has fascinated many researchers around the world. The current review discovers the potential application of lignocellulosic biomass for the production of biofuels. Various pretreatment methods have been widely used to increase the hydrolysis rate and accessibility of biomass. This review highlights recent advances in pretreatment methodologies for the enhanced production of biofuels. Detailed descriptions of the mechanism of biomass processing pathway, optimization, and modeling study have been discussed.

Analysis of physiochemical composition and antioxidant properties between hulls of the genetically modified glyphosate-tolerant soybean and northeast soybean

In this study, the physiochemical and antioxidant properties of the soybean hulls from the genetically modified glyphosate-tolerant soybeans (line 40-3-2) and local cultivar northeast soybeans were investigated. The levels of fat, total phenolic, total extractable pectin and soluble dietary fiber in northeast soybeans hulls were less than that in glyphosate-tolerant soybeans hulls, respectively. The antioxidant capacity of total phenolic, water soluble pectin, and soluble dietary fiber showed that DPPH free radical scavenging activities of glyphosate-tolerant soybeans hulls were 118.23, 57.34 and 197.22 μg AAE/g, which were 2.3, 1.2 and 9.4 times of northeast soybeans hulls, respectively (p < 0.05), and FRAP of glyphosate-tolerant soybeans hulls were 401.67, 747.51 and 328.53 μg AAE/g, which were 1.8, 8.7 and 4.8 times of northeast soybeans hulls (p < 0.05). Glyphosate-tolerant soybeans hulls extract showed the stronger antioxidant activity, which was positively correlated with total phenolic content (r = 0.890, p = 0.001). It provides evidence on developing value-added utilization of hulls, soybean processing by-products, as nutraceuticals or functional food ingredients.

Effects of Heating Temperature on the Properties of Bio-Board Manufactured by Using Soybean Straw

The objective of this paper is to effectively use soybean straw biomass resources and decrease the negative effects of using synthetic resin. Soybean straw was ground through a wet process then hot-pressed to make biodegradable fiberboard (bio-board) without any binder. The effect of heating temperature on mechanical properties and dimensional stability performance of produced bio-board was investigated. Bonding quality and chemical changes of the bio-board were also evaluated using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The moisture content decreased from 12.5% to 3.4% with the increase of heating temperature. Meanwhile, most mechanical properties of bio-board improved. However, an excessive heating temperature, especially at 230 °C, did not significantly promote the improvement of most mechanical properties. However, the dimensional stability performance of the bio-board was greatly improved from 140 °C to 230 °C. Overall, the results showed that bio-board could be made by using soybean straw without any synthetic resin. Heating temperature plays a significant role in affecting the properties of bio-board. The refined bio-board is expected to be used as a packaging material, heat insulation in architecture, and mulch film for agricultural purposes.

Evaluation of Alkali-Pretreated Soybean Straw for Lignocellulosic Bioethanol Production

Soybean straw is a renewable resource in agricultural residues that can be used for lignocellulosic bioethanol production. To enhance enzymatic digestibility and fermentability, the biomass was prepared with an alkali-thermal pretreatment (sodium hydroxide, 121°C, 60 min). The delignification yield was 34.1~53%, in proportion to the amount of sodium hydroxide, from 0.5 to 3.0 M. The lignin and hemicellulose contents of the pretreated biomass were reduced by the pretreatment process, whereas the proportion of cellulose was increased. Under optimal condition, the pretreated biomass consisted of 74.0±0.1% cellulose, 10.3±0.1% hemicellulose, and 10.1±0.6% lignin. During enzymatic saccharification using Cellic® CTec2 cellulase, 10% (w/v) of pretreated soybean straw was hydrolyzed completely and converted to 67.3±2.1 g/L glucose and 9.4±0.5 g/L xylose with a 90.9% yield efficiency. Simultaneous saccharification and fermentation of the pretreated biomass by Saccharomyces cerevisiae W303-1A produced 30.5±1.2 g/L ethanol in 0.5 L fermented medium containing 10% (w/v) pretreated biomass after 72 h. The ethanol productivity was 0.305 g ethanol/g dry biomass and 0.45 g ethanol/g glucose after fermentation, with a low concentration of organic acid metabolites. Also, 82% of fermentable sugar was used by the yeast for ethanol fermentation. These results show that the combination of alkaline pretreatment and biomass hydrolysate is useful for enhancing bioethanol productivity using delignified soybean straw.

Chemical treatment and characterization of soybean straw and soybean protein isolate/straw composite films

This work investigated changes in the chemical composition and structure of soybean straw (SS) treated with alkali (NaOH 5% and 17.5%) and bleached with hydrogen peroxide (H2O2) or sodium hypochlorite (NaOCl). Removal of the amorphous constituents increased the degree of crystallinity and the content of cellulose fibers particularly after reaction with high concentrations of alkali. Treatment with NaOH 17.5% contributed to the allomorph transition from cellulose I to II regardless of the bleaching agent, but H2O2 as bleaching agent promoted more effective delignification. This work also evaluated the potential use of treated and non-treated SS as reinforcement filler in soy protein isolate film (SPI). Films added with treated SS presented higher mechanical resistance, lower elongation at break, and lower solubility in water. Addition of non-treated SS did not affect the properties of the SPI film significantly. The low solubility and the reasonable water vapor permeability of the composite films make them suitable packaging materials for fresh fruit and vegetables.

Enhancement of biohydrogen production from brewers' spent grain by calcined-red mud pretreatment

This paper investigated the utilization of calcined-red mud (CRM) pretreatment to enhance fermentative hydrogen yields from brewers' spent grain (BSG). The BSG samples were treated with different concentrations (0.0-20g/L) of CRM at 55°C for 48h, before the biohydrogen process with heat-treated anaerobic sludge inoculum. The highest specific hydrogen production of 198.62ml/g-VS was obtained from the BSG treated with 10g/L CRM, with the corresponding lag time of 10.60h. Hydrogen yield increments increased by 67.74%, compared to the control tests without CRM. The results demonstrated that the CRM could hydrolyze more cellulose and further provided adequate broth and suitable pH value for efficient fermentative hydrogen. The model-based analysis showed that the modified Gompertz model presented a better fit for the experimental data than the first-order model.

Biomass pretreatments capable of enabling lignin valorization in a biorefinery process

Recent techno-economic studies of proposed lignocellulosic biorefineries have concluded that creating value from lignin will assist realization of biomass utilization into valuable fuels, chemicals, and materials due to co-valorization and the new revenues beyond carbohydrates. The pretreatment step within a biorefinery process is essential for recovering carbohydrates, but different techniques and intensities have a variety of effects on lignin. Acidic and alkaline pretreatments have been shown to produce diverse lignins based on delignification chemistry. The valorization potential of pretreated lignin is affected by its chemical structure, which is known to degrade, including inter-lignin condensation under high-severity pretreatment. Co-valorization of lignin and carbohydrates will require dampening of pretreatment intensities to avoid such effects, in spite of tradeoffs in carbohydrate production.

Thermophilic bio-hydrogen production from corn-bran residue pretreated by calcined-lime mud from papermaking process

This study investigated the use of calcined-lime mud from papermaking process (CLMP) pretreatment to improve fermentative hydrogen yields from corn-bran residue (CBR). CBR samples were pretreated with different concentrations (0-15 g/L) of CLMP at 55°C for 48 h, prior to the thermophilic fermentation with heat-treated anaerobic sludge inoculum. The maximum hydrogen yield (MHY) of 338.91 ml/g-VS was produced from the CBR pretreated with 10 g/L CLMP, with the corresponding lag-phase time of 8.24h. Hydrogen yield increments increased from 27.76% to 48.07%, compared to the control. The CLMP hydrolyzed more cellulose, which provided adequate substrates for hydrogen production.