Fenton pre-treatment of rice straw with citric acid as an iron chelate reagent for enhancing saccharification

Abstract

The Fenton reagent has recently been verified as being effective for lignocellulose pretreatment. However, the Fenton reaction can only work under acidic conditions, leading to severe environmental pollution and increasing the cost for sewage treatment. This has made identification of iron chelates that could enhance Fenton degradation under neutral conditions important. In this study, citric acid, a non-toxic polyhydroxy carboxylic acid, was introduced as an iron chelate in Fenton pre-treatment of rice straw. Results demonstrated that citric acid has the ability to (i) maintain the oxidation capacity of the Fenton reagent under near-neutral conditions, (ii) enhance the degradation of lignin and reduce the crystallinity of rice straw from 0.41 to 0.21, (iii) promote the saccharification of rice straw (the maximum saccharification ratio of 35.7% was two-fold higher than that for the untreated rice straw), and (iv) elevate the maximum activity of b-glucosidase from 0.33 IU mL À1 to 0.61 IU mL À1 . Moreover, the effect of operational parameters such as pH and processing time on the saccharification of rice straw by Fenton pretreatment with and without citric acid has been demonstrated. The findings strongly support Fenton plus citric acid as an efficient and environmentally friendly lignocellulose pretreatment method.

Enhanced biohydrogen production from nutrient-free anaerobic fermentation medium with edible fungal pretreated rice straw

“…6 Conventional lignocellulose pretreatment mainly includes physical, chemical, and combined physicochemical methods (e.g., grinding, ultrasonic, microwave, alkali, acid, stream explosion, organosolv, and ionic liquid). 7 However, most of these approaches are cost-intensive due to high energy and/or chemical requirements, 8 the severe pretreatment conditions induced by acid, alkaline, and high temperature also produce various inhibitory byproducts such as furfural and hydroxymethyl furfural (HMF) that would repress the subsequent fermentation process. 9 Thus, downstream detoxication is needed, which will unquestionable increase the complexity and cost of the whole fermentation process.…”

Study on the Sugar-Producing Effect of High-Temperature Anaerobic Straw Biosaccharification Strain

“…It was proved that the optimal conditions for sugar production of FC811 strain were a temperature of 58.9 • C, pH of 7.21, culture time of 6.60 d, substrate concentration of 5.01 g/L, and yeast powder concentration of 2.15 g/L. The yield of soluble sugar was 3.11 g/L, and the conversion rate of reducing sugar was 62.2%, which is much higher than the previous [41]. The present study results will provide a theoretical basis for subsequent synchronous fermentation of sugar and hydrogen production.…”

Fenton Reaction-Modified Corn Stover To Produce Value-Added Chemicals by Ultralow Enzyme Hydrolysis and Maleic Acid and Aluminum Chloride Catalytic Conversion

“…Figure b–d shows the micromorphology of Fenton-modified CS in the batch reaction. Many eroded sites that formed as holes and cracks were observed on the surface of the Fenton-modified CS . It has been demonstrated that the batch Fenton reaction produced a large amount of hydroxyl radicals instantly, which could destroy the outside structure of lignin and hemicellulose and then get into the internal cellulose structure, causing irreversible damage.…”