A novel sono-assisted acid pretreatment of chili post harvest residue for bioethanol production

Ultrasonic Processing of Food Waste to Generate Value-Added Products

Ultrasonic processing has a great potential to transform waste from the food and agriculture industry into value-added products. In this review article, we discuss the use of ultrasound for the valorisation of food and agricultural waste. Ultrasonic processing is considered a green technology as compared to the conventional chemical extraction/processing methods. The influence of ultrasound pre-treatment on the soluble chemical oxygen demand (SCOD), particle size, and cell wall content of food waste is first discussed. The use of ultrasonic processing to produce/extract bioactives such as oil, polyphenolic, polysaccharides, fatty acids, organic acids, protein, lipids, and enzymes is highlighted. Moreover, ultrasonic processing in bioenergy production from food waste such as green methane, hydrogen, biodiesel, and ethanol through anaerobic digestion is also reviewed. The conversion of waste oils into biofuels with the use of ultrasound is presented. The latest developments and future prospective on the use of ultrasound in developing energy-efficient methods to convert food and agricultural waste into value-added products are summarised.

Removal of inhibitory furan aldehydes in lignocellulosic hydrolysates via chitosan-chitin nanofiber hybrid hydrogel beads

To obtain fermentable sugars from lignocellulose, various inhibitors, especially furan aldehydes, are usually generated during the pretreatment process. These inhibitors are harmful to subsequent microbial growth and fermentation. In this study, a novel detoxification strategy was proposed to remove 5-hydroxymethylfurfural (HMF) and furfural while retaining glucose and xylose using self-prepared chitosan-chitin nanofiber hybrid hydrogel beads (C-CNBs). After C-CNBs treatment, the removal rates of HMF and furfural from sugarcane bagasse hydrolysates reached 63.1% and 68.4%, while the loss rates of glucose and xylose were only 6.3% and 8.2%, respectively. Two typical industrial strains grew well in monosaccharide-rich detoxified hydrolysates, with a specific growth rate at least 4.1 times that of undetoxified hydrolysates. Furthermore, adsorption mechanism analysis revealed that the Schiff base reaction and mesopore filling were involved in furan aldehyde adsorption. In total, C-CNBs provide an efficient and practical approach for the removal of furan aldehydes from lignocellulosic hydrolysates.

Lignocellulose in future biorefineries: Strategies for cost-effective production of biomaterials and bioenergy

Lignocellulosic biomass has been emerging as a biorefinery precursor for variety of biofuels, platform chemicals and biomaterials because of its specific surface morphology, exceptional physical, chemical and biological characteristics. The selection of proper raw materials, integration of nano biotechnological aspects, and designing of viable processes are important to attain a cost-effective route for the development of valuable end products. Lignocellulose-based materials can prove to be outstanding in terms of techno-economic viability, as well as being environmentally friendly and reducing effluent load. This review should facilitate the identification of better lignocellulosic sources, advanced pretreatments, and production of value-added products in order to boost the future industries in a cleaner and safer way.

Application of biomass derived products in mid-size automotive industries: A review

The automotive industry is directly affected by the shortage of fossil fuels and the excessive pollution resulting from crude oil-based fuels has many adverse effects on the environment. The search for a greener and sustainable source of materials and fuels to power automobiles has ultimately led to the usage of biomass and biobased sources as the main precursor due to its graft availability and renewability. Biobased fuels developed have been shown to easily blend in with the existing automobile engines and to provide sustainable performance. Similarly, the usage of various biobased polymers, plastics, and composite materials as the structural materials for the construction of automobiles instead of crude oil sources have shown to be invaluable. The powering of automobiles with electricity is the future of the transportation industry to address the greenhouse gas emissions caused by fossil fuels. Hence, biobased lithium-ion batteries and supercapacitors have started to enter the mid-sized automotive industry. However, extensive commercialization of biobased products application in the automotive sector is underdeveloped. Hence it is customary to assess the various drawbacks of using biobased materials and identify the correct pathway for new research and development in this field. Therefore, this review covers various applications of biobased products in the automotive industries and mentions the active researches going on in this field to replace petroleum and crude oil-based sources with biobased sources.

Development of artificial neural network tools for predicting sugar yields from inorganic salt-based pretreatment of lignocellulosic biomass

This study developed two Artificial Neural Network (ANN) tools for predicting sugar yields from inorganic salt-based pretreatment of lignocellulosic biomass. Pretreatment data from 90 experimental runs with 8 different input conditions were used to develop a microwave-based and a steam-based model. Both models exhibited high coefficients of determination (R²) of 0.97. Knowledge extraction revealed reducing sugar yields from the steam- and microwave-based models exhibited high sensitivity to both salt and alkali concentration. These models may be employed as initial screening tools in lignocellulosic bioprocesses, thereby potentially enhancing the economic and productivity of lignocellulosic-based bioprocesses.

Strategies for enhancing microbial tolerance to inhibitors for biofuel production: A review

Using lignocellulosic biomass for the production of renewable biofuel provides a sustainable and promising solution to the crisis of energy and environment. However, the processes of biomass pretreatment and biofuel fermentation bring a variety of inhibitors to microbial strains. These inhibitors repress microbial growth, decrease biofuel yields and increase fermentation costs. The production of biofuels from renewable lignocellulosic biomass relies on the development of tolerant and robust microbial strains. In recent years, the advancement of tolerance engineering and evolutionary engineering provides powerful platform for obtaining host strains with desired tolerance for further metabolic engineering of biofuel pathways. In this review, we summarized the inhibitors derived from biomass pretreatment and biofuel fermentation, the mechanisms of inhibitor toxicity, and the strategies for enhancing microbial tolerance.

Ultrasound-assisted biological conversion of biomass and waste materials to biofuels: A review

Ultrasound irradiation has been gaining increasing interests over the years to assist biological conversion of lignocellulosic biomass and waste materials to biofuels. As such, this study reviewed the different effects of sonication on pre-treatment of lignocellulosic biomass and waste materials prior to biofuel production. The mechanisms of ultrasound irradiation as a pre-treatment technique were initially described and the impacts of sonication on disruption of lignocellulosic materials, alteration of the crystalline lattice structure of cellulose molecules, solubilisation of organic matter, reducing sugar production and enzymatic hydrolysis were then reviewed. Subsequently, the influences of ultrasound irradiation on bio-methane, bio-hydrogen and bio-ethanol production were re-evaluated, with most studies reporting enhanced biofuel production from anaerobic digestion or fermentation processes. Nonetheless, despite its positive impacts on biofuel production, sonication was found to be energetically inefficient based on the lab-scale studies reviewed. To conclude, this study reviewed some of the challenges of ultrasound irradiation for enhanced biofuel production while outlining some areas for further research.

Optimization of a novel sequential alkalic and metal salt pretreatment for enhanced delignification and enzymatic saccharification of corn cobs

This study presents a sequential sodium phosphate dodecahydrate (Na₃PO₄·12H₂O) and zinc chloride (ZnCl₂) pretreatment to enhance delignification and enzymatic saccharification of corn cobs. The effects of process parameters of Na₃PO₄·12H₂O concentration (5-15%), ZnCl₂ concentration (1-5%) and solid to liquid ratio (5-15%) on reducing sugar yield from corn cobs were investigated. The sequential pretreatment model was developed and optimized with a high coefficient of determination value (0.94). Maximum reducing sugar yield of 1.10±0.01g/g was obtained with 14.02% Na₃PO₄·12H₂O, 3.65% ZnCl₂ and 5% solid to liquid ratio. Scanning electron microscopy (SEM) and Fourier Transform Infrared analysis (FTIR) showed major lignocellulosic structural changes after the optimized sequential pretreatment with 63.61% delignification. In addition, a 10-fold increase in the sugar yield was observed compared to previous reports on the same substrate. This sequential pretreatment strategy was efficient for enhancing enzymatic saccharification of corn cobs.

Potential of Brachiaria mutica (Para grass) for bioethanol production from Loktak Lake

The aim of present study was to evaluate feasibility of using the Para grass as feedstock for production of bioethanol. Process involved the pretreatment with dilute acid or alkali and followed by enzymatic saccharification with commercial cellulase. Maximum sugar release of 696mg/g was obtained from 10% biomass loading and 0.5% w/v of alkali whereas in the case of acid pretreatment maximum sugar of 660mg/g was obtained from 20% biomass loading and 2% w/v acid loading. Results showed that Para grass utilization as a biorefinery feedstock can be a potential strategy to address the sustainable utilization of this invasive grass thereby keeping its population in check in the Loktak Lake.

Development of a novel ultrasound-assisted alkali pretreatment strategy for the production of bioethanol and xylanases from chili post harvest residue

A novel ultrasound-assisted alkali pretreatment strategy was developed which could effectively remove lignin and hemicelluloses and improve the sugar yield from chili post harvest residue. Operational parameters that affect the pretreatment efficiency were studied and optimized. Inhibitor analysis of the hydrolyzate revealed that major fermentation inhibitors like furfural, 5-hydroxymethyl furfural as well as organic acids like citric acid, succinic acid and propionic acid were absent. Hence fermentation can be carried out without detoxification of the hydrolyzate. Changes in structural properties of the biomass were studied in relation to the pretreatment process using Scanning Electron Microscopy (SEM) and the changes in chemical composition were also monitored. The biomass pretreated with the optimized novel method could yield 0.428g/g of reducing sugars upon enzymatic hydrolysis. The hydrolyzate obtained by this novel pretreatment strategy was found to be suitable for bioethanol and xylanase production.

Microwave-assisted inorganic salt pretreatment of sugarcane leaf waste: Effect on physiochemical structure and enzymatic saccharification

This paper presents a method to pretreat sugarcane leaf waste using microwave-assisted (MA) inorganic salt to enhance enzymatic saccharification. The effects of process parameters of salt concentration, microwave power intensity and pretreatment time on reducing sugar yield from sugarcane leaf waste were investigated. Pretreatment models based on MA-NaCl, MA-ZnCl₂ and MA-FeCl₃ were developed with high coefficients of determination (R² >0.8) and optimized. Maximum reducing sugar yield of 0.406g/g was obtained with 2M FeCl₃ at 700W for 3.5min. Scanning electron microscopy (SEM), Fourier Transform Infrared analysis (FTIR) and X-ray diffraction (XRD) showed major changes in lignocellulosic structure after MA-FeCl₃ pretreatment with 71.5% hemicellulose solubilization. This regime was further assessed on sorghum leaves and Napier grass under optimal MA-FeCl₃ conditions. A 2-fold and 3.1-fold increase in sugar yield respectively were observed compared to previous reports. This pretreatment was highly effective for enhancing enzymatic saccharification of lignocellulosic biomass.

Microbial biodiesel production from oil palm biomass hydrolysate using marine Rhodococcus sp. YHY01

The effect of various biomass derived inhibitors (i.e. furfural, hydroxymethylfurfural (HMF), vanillin, 4-hydroxy benzaldehyde (4-HB) and acetate) was investigated for fatty acid accumulation in Rhodococcus sp. YHY 01. Rhodococcus sp. YHY01 was able to utilize acetate, vanillin, and 4-HB for biomass production and fatty acid accumulation. The IC₅₀ value for furfural (3.1mM), HMF (3.2mM), vanillin (2.0mM), 4-HB (2.7mM) and acetate (3.7mM) was calculated. HMF and vanillin affect fatty acid composition and increase saturated fatty acid content. Rhodococcus sp. YHY 01 cultured with empty fruit bunch hydrolysate (EFBH) as the main carbon source resulted in enhanced biomass (20%) and fatty acid productivity (37%), in compression to glucose as a carbon source. Overall, this study showed the beneficial effects of inhibitory molecules on growth and fatty acid production, and support the idea of biomass hydrolysate utilization for biodiesel production by avoiding complex efforts to remove inhibitory compounds.