https://cyberleninka.org/article/n/1199846.pdf

Agro-industrial lignocellulosic biomass a key to unlock the future bio-energy: A brief review

In response to the scarcity of non-renewable energy sources, sustainable and renewable biofuels from biomass have gained utmost attention. Utilization of lignocellulosic biomass for production of varied energy forms (second generation fuels) like biogas, biodiesel, bioethanol, etc has increased in the past decade. Their properties of being naturally abundant and easily accessible throughout the year, makes them an attractive energy alternative. Efficient pretreatment techniques for effective transformation of lignocelluloses to varied products, by increasing digestibility of celluloses and hemicelluloses can be achieved through acid, alkali treatment, enzymatic hydrolysis, and steam explosion. Idea behind optimizing pretreatment protocol is to maximize release of monosaccharide sugars for conversion to value added products. Tailoring of hydrolytic enzymes through various approaches is well accepted for increasing specific activity of particular enzymatic reaction and can also be clubbed with other pretreatment processes minimizing chemical usage. We at our laboratory are working on optimization of process parameters for enhancing efficiency of saccharification process to obtain maximal monosaccharide sugars that can be converted to bioethanol. Present review compiles various approaches made by prominent scientists for efficient utilization of celluloses and hemicelluloses for ethanol production and also describes recent advanced techniques utilized for the same. Greater emphasis has been led on comparative study on utilization of simple sugars by bacteria and fungi and effect of consolidated bioprocess system on ethanol production from varied agro-industrial wastes.

Recent advances in second generation bioethanol production: An insight to pretreatment, saccharification and fermentation processes

Biological pretreatment (BP) is a promising approach for treating microalgae and lignocellulosic biomass (LCB) during biofuels production that uses mostly fungal and bacterial strains or their enzymes. Pretreatment with fungi requires long incubation time (weeks to months), whereas, bacterial and enzymatic pretreatments can be completed by only a few hours to days. Nevertheless, fungal pretreatment especially with white-rot fungi (WRF) is predominantly used in BP of biomass for its high efficiency and downstream yields. According to the recent reports, delignification of LCB by WRF may vary between 3% and 72% with a maximum 120% increase in the biofuel yield. Compared to the untreated microalgae biomass, the downstream yields of the respective biofuels were found to be increased by 22–159% after bacterial pretreatment, while enzymatic pretreatment improved as much as 485% of the final yield. Despite the results are promising, exploitation of BP on large scale is still bottlenecked by some technoeconomic hurdles, which need to be overcome through further fundamental and applied researches. This paper presents a comprehensive and in-depth review on BP for LCB and microalgae biomass by focusing on the relevant overviews and perspectives, technological approaches, mechanisms, influencing factors, and recent research progresses. Finally, challenges and future outlooks are discussed in the concluding sections.

Recent advances in biological pretreatment of microalgae and lignocellulosic biomass for biofuel production

Lignocellulose: A Sustainable Material to Produce Value-Added Products With a Zero Waste approach-A Review

The development and production of fossil fuel alternatives have become one of the main focal points in recent investigations. Lignocellulosic biomass is a renewable source of fermentable sugars for second-generation biofuels and chemicals via biotechnological pathways. However, the presence of lignin and hemicellulose in lignocellulosic biomass makes it difficult for the biomass to be hydrolyzed or digested during fermentation. Thus, effective biomass pretreatment is vital. The present review shows that chemical pretreatment is the current preferred method to obtain high sugar yields at low cost, with dilute acid and alkaline hydrolysis as the two most reported technologies. Dilute acid favours hydrolysis of the hemicelluloses whereas alkaline hydrolysis targets the lignin fraction. Both methods have merits and demerits, and have been combined with other treatments such as hydrothermal and enzymatic hydrolysis. Further investigation is required to improve the pretreatment processes and to ensure the economic viability of bioconversion.

Typical conversion of lignocellulosic biomass into reducing sugars using dilute acid hydrolysis and alkaline pretreatment

Alkali and enzymatic delignification of sugarcane bagasse to expose cellulose polymers for saccharification and bio-ethanol production

Bacterial cellulose-assisted de-lignified wheat straw-PVA based bio-composites with novel characteristics.

Valorization of lignocellulosic waste residues in the development of potential biodegradable composites has been of recent research interest. Recent research has shown that wheat straw can be used as a reinforcement material for the synthesis of novel polyvinyl alcohol (PVOH)-based composites. However, certain pretreatment methodology needs to be used for the selective removal of the lignin component. The de-lignification of native wheat straw was performed using an in-house isolated ligninolytic consortium. The bio-composites were developed using the de-lignified wheat straw along with PVOH as the matrix phase and glycerol as a plasticizer via a compression molding technique. In this study, a structural analysis by Fourier transform infrared spectroscopy (FT-IR) showed that the enzymatic treatment led to noticeable changes in the chemical structure of the materials used. A dynamic mechanical analysis (DMA) of the composites revealed an increase in the tensile strength of the sample from 46.1 MPa ± 0.1 MPa to 53.0 MPa ± 0.9 MPa, upon the addition of the plasticizer. Also, there was a noticeable increase in the tensile modulus of composites from 2,130 MPa to 4,520 MPa, respectively. Topographical features of the newly synthesized PVOH-based bio-composites were observed using scanning electron microscopy.

https://ojs.cnr.ncsu.edu/index.php/BioRes/article/download/BioRes_12_2_2830_Ahmad_Wheat_Straw_PVOH_Biocomposites/5149

Enzyme-treated Wheat Straw-based PVOH Bio-composites: Development and Characterization

Lignin biodegradation is an attractive approach for producing value-added products These valuable products are produced by the processing and refining of lignocellulosic residues A set of ligninolytic enzymes including lignin peroxidase (LiP), manganese-dependent peroxidase (MnP), and laccase (Lac) were individually produced from Ganoderma lucidum, Trametes versicolor, and Pleurotus ostreatus Solid state fermentation under pre-optimized culture conditions with varying ratios of enzymes were used for the delignification of lignocellulosic biomass residues The fungal enzymes were purified in four steps including ammonium sulfate precipitation, dialysis, ion exchange chromatography, and gel filtration chromatography The purified enzymes were subsequently used in varying ratios (with each containing 200 U/mL) for the delignification of wheat straw, sugarcane bagasse, and rice straw The consortium of enzymes caused the removal of 585%, 46%, and 52% of the lignin from the wheat straw, sugarcane bagasse, and rice straw, respectively, at LiP: MnP: Lac ratios of 1:2:2, 1:1:2, and 2:1:2 The best delignification was observed in wheat straw (585%), exposing 7654% cellulose content The results suggested that the ligninolytic enzymes are effective catalysts for the selective partial delignification of lignocellulosic biomass residues After delignification these lignocellulosic residues could be utilized as cost-effective substrates for the production of enzymes, biofuels, and other industrially significant products

https://ojs.cnr.ncsu.edu/index.php/BioRes/article/download/BioRes_11_4_10511_Ahmad_Novel_Approach_Delignify_Lignocellulosic/4893

Zanib Ahmad

Papers

Lignocellulose: A Sustainable Material to Produce Value-Added Products With a Zero Waste approach-A Review

Alkali and enzymatic delignification of sugarcane bagasse to expose cellulose polymers for saccharification and bio-ethanol production

Bacterial cellulose-assisted de-lignified wheat straw-PVA based bio-composites with novel characteristics.

Enzyme-treated Wheat Straw-based PVOH Bio-composites: Development and Characterization

A Novel Approach to Delignify Lignocellulosic Materials by Using Ligninolytic Enzyme Consortium