Enhanced Saccharification and Fermentation of Rice Straw by Reducing the Concentration of Phenolic Compounds Using an Immobilized Enzyme Cocktail

Abstract

The production of bioethanol from rice straw can contribute to the rural economy and provide clean fuel in a sustainable manner. However, phenolic compounds, which are mostly produced during acid pretreatment of biomass, act as inhibitors of fermenting microorganisms. Laccase is well known for its ability to oxidize lignin and phenolic compounds derived from lignocellulosic biomass. In the present study, an immobilized enzyme cocktail containing laccase was isevaluated in regard to its ability to enhance the saccharification and fermentation processes by reducing the amount of phenolic compounds produced. Saccharification of rice straw with the laccase‐supplemented immobilized enzyme cocktail reduced phenolic compounds by 73.8%, resulting in a saccharification yield of 84.6%. In addition, improved yeast performance was is noted during the fermentation process, resulting in a 78.3% conversion of sugar into ethanol with an ethanol productivity of 0.478 g/L/h. To the best of our knowledge, this is the first description of the use of an immobilized enzyme cocktail comprised of Celluclast 1.5L, β‐glucosidase, and laccase for the production of bioethanol from rice straw. This study details a potential approach to producing biofuels from agricultural biomass, the applicability of which can be improved through up‐scaling.

Enzymatic Pretreatment with Laccases from Lentinus sajor-caju Induces Structural Modification in Lignin and Enhances the Digestibility of Tropical Forage Grass (Panicum maximum) Grown under Future Climate Conditions

“…Lignocellulosic biomasses are mainly composed of carbohydrate polymers like cellulose and hemicellulose, which are hindered by lignin that is a heteropolymer composed of three main phenylpropane units: p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) [4]. Due to the close association of lignin with cellulose microfibrils forming lignincarbohydrate complexes (LCCs), this polymer represents a significant barrier in the enzymatic conversion of polysaccharides into sugars that can be further fermented to produce second-generation ethanol or added value green chemicals.…”

Bioelectrochemical Detoxification of Phenolic Compounds during Enzymatic Pre-Treatment of Rice Straw

“…The activity of celluclast 1.5 L was evaluated and expressed in Filter Paper activity Units (FPUs). Laccase, BGL, and celluclast enzyme activities were measured as previously described [19]. One FPU is defined as the amount of enzyme that releases 1 μmol of glucose-equivalents from hydrolysis of Whatman No.…”

“…The mix was then placed in a steam explosion reactor and incubated at 121°C for 60 min. This pre-treated rice straw was filtered and washed with distilled water until its pH was neutralized [19]. Next, it was incubated in an oven at 60ºC until it completely dried up, as assessed by its weight not decreasing any further, and then used in the experiments.…”

Biosynthesis of Lactobionic Acid in Whey-Containing Medium by Microencapsulated and Free Bacteria of Pseudomonas taetrolens

“…Utilizing this freely available waste-water along with biodiesel industry waste-crude glycerol for bio-hydrogen production is being reported by Prakash et al (2018) [22]. The study of Kumar et al (2019) [23] details a potential approach to producing biofuels from agricultural biomass, the applicability of which can be improved through upscaling. In the present study, an immobilized enzyme cocktail containing laccase was isevaluated in regard to its ability to enhance the saccharification and fermentation processes by reducing the amount of phenolic compounds produced.…”