Combined ensiling and hydrothermal processing as efficient pretreatment of sugarcane bagasse for 2G bioethanol production

Subcritical Water Pretreatment for the Efficient Valorization of Sorghum Distillery Residue for the Biorefinery Platform

The depletion of fossil fuels is resulting in an increased energy crisis, which is leading the paradigm shift towards alternative energy resources to overcome the issue. Lignocellulosic biomass or agricultural residue could be utilized to produce energy fuel (bioethanol) as it can resolve the issue of energy crisis and reduce environmental pollution that occurs due to waste generation from agriculture and food industries. A huge amount of sorghum distillery residue (SDR) is produced during the Kaoliang liquor production process, which may cause environmental problems. Therefore, the SDR generated can be utilized to produce bioethanol to meet current energy demands and resolve environmental problems. Using a central composite experimental design, the SDR was subjected to hydrothermal pretreatment. The conditions selected for hydrothermal pretreatment are 155 °C, 170 °C, and 185 °C for 10, 30, and 50 min, respectively. Based on the analysis, 150 °C for 30 min conditions for SDR hydrothermal pretreatment were selected as no dehydration product (Furfural and HMF) was detected in the liquid phase. Therefore, the pretreated slurry obtained using hydrothermal pretreatment at 150 °C for 30 min was subjected to enzymatic hydrolysis at 5% solid loading and 15 FPU/gds. The saccharification yield obtained at 72 h was 75.05 ± 0.5%, and 5.33 g/L glucose concentration. This non-conventional way of enzymatic hydrolysis eliminates the separation and detoxification process, favoring the concept of an economical and easy operational strategy in terms of biorefinery.

Ensiling pretreatment with two novel microbial consortia enhances bioethanol production in sterile rice straw

The present study extracts and enriches cellulolytic microbial consortia from yak (Bos grunniens) and evaluates their effects on the fermentation profile and bioethanol yield in rice straw silage. Two microbial consortia (CF and PY) with high cellulolytic activity were isolated and observed to be prone to utilize natural carbon sources. Two consortia were introduced with and without combined lactic acid bacteria (CLAB) to rice straw for up to 60 days of ensiling, and their application notably decreased the levels of structural carbohydrates and pH values of rice straw silages. Treatments that combining microbial consortia and CLAB resulted in the highest levels of lactic acid, water soluble carbohydrates, mono- and disaccharides, and lignocellulose degradation, with PY + CLAB group yielding the highest bioethanol production. The microbial consortia identified herein exhibit great potential for degrading fibrous substrates, and their combination with CLAB provides a feasible way to efficiently use rice straw for bioethanol production.

Cost-effective production of biocatalysts using inexpensive plant biomass: a review

Enzymes are the complex protein moieties, catalyze the rate of chemical reactions by transforming various substrates to specific products and play an integral part in multiple biochemical cycles. Advancement in enzyme research and its integration with industries have reformed the biotech industries. It provides a superior monetary and ecological exchange to traditional material measures in an efficient and environmentally sustainable manner. The cost-effective production of pure and highly active enzymes is still a challenge for the biocatalyst industries. The use of high purity substrates further raises the cost of a typical biocatalyst. The use of low-cost plant-based biomasses as an enticing and sustainable substrate for enzyme production is the most cost-effective approach to these problems. Given the relevance of biomass as a substrate for enzyme development, this review article focuses on the key source, composition and major enzyme generated using various biomass residues. Furthermore, the difficulties associated with the use of biomass as a substrate and technical developments in this area, are also addressed. The use of waste biomass as a substrate lowers the ultimate cost for the production of biocatalysts while simultaneously reduces the waste burden from the environment.

Synergism of sweeping frequency ultrasound and deep eutectic solvents pretreatment for fractionation of sugarcane bagasse and enhancing enzymatic hydrolysis

Sugarcane bagasse (SCB) is an abundant agricultural waste in China and the conversion of the waste into plethora of useful resources is very vital. To achieve this, fractionation of the waste is highly important in the biomass biorefinery. The present study aims at investigating the synergistic role of deep eutectic solvents (DES) with sweeping frequency ultrasound (SFUS) and fixed frequency ultrasound (FFUS) in the fractionation of SCB to enhance the enzymatic saccharification process. Therefore, the effects of ultrasound (US) and DES conditions on the pretreatment efficiency were investigated. Under optimum SCB pretreatment conditions, FFUS (40 kHz, 60 min) + DES (choline chloride (ChCl)-lactic acid (LA), 120 °C, 3 h) and SFUS (40 kHz, 60 min) + DES (ChCl-LA, 120 °C, 3 h), the lignin removal rates were 80.13 and 85.62%, respectively. The hemicellulose removal rates were 78.08 and 90.46%, respectively; and the contents of glucose, xylose and arabinose in the liquid fractions after FFUS + DES pretreatment were 7.07, 17.95 and 3.01%, respectively. However, the yield of glucose, xylose, and cellobiose after enzymatic hydrolysis of the SFUS + DES pretreated SCB were 86.76, 38.68, and 20.76%. Analytical studies revealed that the SFUS + DES pretreatment can effectively destroy the ultrastructure of SCB and reduce the crystallinity of cellulose. Furthermore, the mechanism of pretreatment with SFUS + DES was proposed, which confirmed the excellent performance of SFUS + DES. Thus, the application of SFUS + DES pretreatment was able to improve the removal of lignin and hemicellulose from SCBs.

Effects of NaOH-catalyzed organosolv pretreatment and surfactant on the sugar production from sugarcane bagasse

In this study, NaOH-catalyzed organosolv pretreatment with different loading of NaOH (0-10%) was proposed to disrupt the recalcitrant structure by degrading lignin, reserve the majority of cellulose and hemicellulose, and improve the enzymatic efficiency of sugarcane bagasse. It was found that the higher loading of NaOH during organosolv pretreatment yielded more glucose, and the synergistic performance of NaOH and ethanol on enzymolysis was superior to that pretreated with only NaOH and only ethanol during two-step pretreatment. Furthermore, Tween 80 was added to determine its influence on enzymolysis after NaOH-catalyzed organosolv pretreatment, leading to the highest glucose yield of 95.1% at 24 h, which saved 2/3 hydrolysis time while generating the similar glucose yield comparing with that without Tween 80. However, the increased yields of glucose by adding Tween 80 were decreased as hydrolysis time was prolonged from 6 h to 24 h.

Vacuum-assisted black liquor-recycling enhances the sugar yield of sugarcane bagasse and decreases water and alkali consumption

Black liquor (BL) remains a critical problem during alkaline pretreatment. To solve this issue, a novel pretreatment strategy termed vacuum-assisted black liquor-recycling pretreatment, was established to pretreat sugarcane bagasse (SCB). Firstly, SCB was pretreated with 2% NaOH at 121 °C for 1 h under vacuum conditions. The produced BL was used for subsequent pretreatments after pH recovery with NaOH. The pretreated SCBs were subject to enzymatic hydrolysis and separate hydrolyzation and fermentation (SHF) without washing to neutral pH. BL was recycled on seven occasions. The results indicated that glucose yields did not significantly differ between pretreatment with NaOH and recovered BL. The enzymatic hydrolysis and the fermentation resulted in maximum 0.35 g/g of glucose yield and 116.5 g/kg of ethanol yield respectively. Compared with conventional pretreatment with NaOH, the VABLR method showed high conversion rates of cellulose into monosaccharaides, whilst preserving ~20% and ~46% of alkali and water usage, respectively.

Review on Bioenergy Storage Systems for Preserving and Improving Feedstock Value

Long-term storage is a necessary unit operation in the biomass feedstock logistics supply chain, enabling biorefineries to run year-round despite daily, monthly, and seasonal variations in feedstock availability. At a minimum, effective storage approaches must preserve biomass. Uncontrolled loss of biomass due to microbial degradation is common when storage conditions are not optimized. This can lead to physical and mechanical challenges with biomass handling, size reduction, preprocessing, and ultimately conversion. This review summarizes the unit operations of dry and wet storage and how they may contribute to preserving or even improving feedstock value for biorefineries.

What Has Been the Focus of Sugarcane Research? A Bibliometric Overview

Sugarcane is one of the main crops worldwide, and it has an important impact on environmental issues. A bibliometric mapping analysis of the research on sugarcane was carried out, using data on the titles, abstracts, and keywords of articles published in leading journals and other peer-reviewed documents available in the SCOPUS database from 1858 to 2019 (27 August), and this was subsequently analyzed with the software VOSviewer. The three most important countries that publish research and were most-cited regarding sugarcane were Brazil, the USA, and India. The analysis of the co-occurrence of terms shows that the main research areas were sugarcane bagasse and terms related to bioenergy, and on a second level of relevance agronomy topics related to increasing crop yields. This first attempt to visualize the abundance of publications regarding sugarcane in their totality is in itself a good starting point for further scientific discussion.