Delignification Of Rice Straw Research Articles

Biodegradation potential and ligninolytic enzyme activity of two locally isolated Panus tigrinus strains on selected agro-industrial wastes

The degradation potential and ligninolytic enzyme production of two isolated Panus tigrinus strains (M609RQY and M109RQY) were evaluated in this study. These strains were grown on three selected abundant agro-industrial wastes (rice straw; rice husk and cassava peel) under solid-state fermentation conditions. Degradation potential was determined by analyzing the chemical composition of the selected substrates before and after fermentation along with ligninolytic enzyme production. The strain M609RQY led to the highest lignin degradation of 40.81% on cassava peel, 11.25% on rice husk and 67.96% on rice straw. Both strains significantly increased the protein content of cassava peel. Rice husk stimulated maximum laccase (2556 U/L) and lignin peroxidase (24 U/L) production by the strains M109RQY and M609RQY, respectively. Furthermore, cassava peel stimulated maximum manganese-dependent peroxidase (141 U/L) production by the strain M109RQY. The de-lignified rice straw and the nutritionally-improved cassava peel could serve as potential animal feed supplements.

Delignification of Rice Straw with Ligninase from Novel Penicillium sp. strain apw-tt2 for Biopulping

Study of biodelignification of rice straw was investigated by using a fungus isolated from indigenous the straw. Identification of the fungus was characterized by 18s rRNA sequencing and included in the new species of Penicillium sp. strain apw-tt2. Ligninase production and cell growth was observed in incubation condition of Submerged Fermentation (SmF). Optimizations of the enzyme production condition were carried out by altering pH and temperature of the incubation medium. The results showed that the optimum conditions for biopulping are at 40˚C and pH 5. High ligninase production was observed at Day 4 with activity 571 U/ml with degraded lignin 66.3%. The quality of pulp showed that the new species is very effective in delignifying rice straw for pulping.

Novel cellulase recycling method using a combination of Clostridium thermocellum cellulosomes and Thermoanaerobacter brockii β-glucosidase

This report describes a novel recycling method utilizing a combination of Clostridium thermocellum cellulosomes and Thermoanaerobacter brockii β-glucosidase (CglT). To recover cellulosomes and CglT through re-binding to additional cellulose, a chimeric CBM3–CglT was created by fusing carbohydrate binding module (CBM3) from the scaffolding protein CipA into the N-terminal region of CglT. When a recycling test using cellulosomes and CBM3–CglT was performed on microcrystalline cellulose, the process was capable of 4 rounds of recycling (1%w/vcellulose/round). Although irreversible absorption of cellulosomes and CBM3–CglT into the residues was observed when ammonia-pretreated rice straw and delignified rice straw was used as substrates, a maximum of 2 and 4 recycling rounds (1%w/vglucan/round) were achieved, respectively, consistent with a 70% saccharification rate. This novel recycling method using cellulosomes and CBM3–CglT has great potential as an effective lignocellulose degradation system.

Atmospheric Acetic Acid Pulping of Rice Straw IV: Physico-Chemical Characterization of Acetic Acid Lignins from Rice Straw and Woods. Part 1. Physical Characteristics

Summary Lignins obtained by atmospheric acetic acid delignification of rice straw, birch and fir were characterized by molecular weight, solubility and thermomechanical analysis, and by ultraviolet (UV), Fourier transform infra-red (FTIR) and 13C-NMR spectroscopy. Rice straw lignins (rice lignins) were very different from birch and fir lignins. The former was difficult to dissolve in most tested solvents and infusible on heating, while the latter had a good solubility and fusibility. FTIR spectra indicated that the rice lignins had more conjugated and fewer unconjugated carbonyl groups than the wood lignins. 13C-NMR spectra showed that rice lignins had more polysaccharides associated to the lignin and more p-coumaric and ferulic acid than the wood lignins. Concentrations of acetic acid and choice of catalyst (sulfuric or hydrochloric acid) had a considerable effect on the characteristics of rice lignins. Rice lignin obtained with 90% acetic acid than that obtained with 80% acetic acid, and the lignin obtained with sulfuric acid as catalyst than that obtained with hydrochloric acid, had lower molecular weight, better solubility, lower glass-transition temperature and lower UV absorptivity. 80% acetic acid delignified rice straw less effectively than 90% acetic acid.

Continuous Simultaneous Saccharification and Fermentation of Delignified Rice Straw by a Combination of Two Reversibly Soluble-Autoprecipitating Enzymes and Pentose-Fermenting Yeast Cells.

Direct ethanol production from delignified rice straw was performed continuously using a combination of two reversibly soluble-autoprecipitating enzymes, [Meicelase and Cellulase Y-NG were individually immobilized on hydroxypropyl methylcellulose acetate succinate (AS-L)] and Pichia stipitis cells. Cellulase Y-NG immobilized on AS-L (X-AS) as well as Meicelase immobilized on AS-L (M-AS) proposed previously (Hoshino et al., 1994) exhibited a sharper response for the solubility depending on the pH changes; insoluble below 3.5 and soluble above 5.0. When delignified rice straw was hydrolysed using two immobilized enzymes at a ratio of X-AS/M-AS = l, the amount of soluble sugars obtained was higher than that using M-AS alone. Moreover, both immobilized enzymes in an insoluble state had good self-sedimentation properties and were coprecipitated with a large portion of P. stipitis cells.Ethanol production was performed continuously by a reactor system equipped with a mixing vessel and a separation vessel. Both immobilized enzymes and the yeast cells were separated continuously from a solution containing ethanol by co-precipitation in the separation vessel and they was returned to a main reactor for reuse. In continuous ethanol production from the rice straw, high ethanol productivity of up to 0.113 kg/(m3·h) was achieved at a dilution rate of 0.050 h-1. This continuous fermentation system suggests potential for effective ethanol production from delignified rice straw.

Operational strategies in vacuum-coupled SSF for conversion of lignocellulose to ethanol

The effects of vacuum cycling time on simultaneous saccharification and fermentation (SSF) of cellulose to ethanol were investigated in a 30-l reactor using mixed enzyme and a thermotolerant yeast Candida acidothermophilum. Lower vacuum cycling times (15 min cycle -1) were found to be energetically more efficient than the ones with higher duration cycles (60 min cycle -1) for conversion of delignified rice straw cellulose to ethanol. A theory has been proposed to explain the enhancement of ethanol volatility in SSF.

Production of soluble sugar from cellulosic materials by repeated use of a reversibly soluble‐autoprecipitating cellulase

A reversibly soluble-autoprecipitating cellulase was prepared by covalently immobilizing Meicelase on an enteric coating polymer (AS-L, hydroxypropyl methylcellulose acetate succinate). The immobilized enzyme (M-AS) was reversibly soluble-insoluble depending on the pH of the reaction medium. Moreover, the enzymatic activity of M-AS, in a soluble state, for microcrystalline cellulose was higher than that of the conventional solid immobilized enzyme. On the other hand, M-AS, in an insoluble state, and good properties of self-sedimentation, and a large portion of M-AS spontaneously precipitated for about 15 min at pH 3.8. In the repeated hydrolysis of rice straw, delignified with sodium hydroxide using a bioreactor with a conical bottom, M-AS was separated batchwise from a production solution by self-sedimentation in a conical bottom of the bioreactor. When delignified, rice straw was hydrolyzed repeatedly by reuse of M-AS; the total amount of soluble sugar produced from 5 g of delignified rice straw was 2.7 g. Further, by the hydrolysis method with repeated removal of reaction inhibitors (soluble sugar), the time required for converting the same amount of delignified rice straw to soluble sugar was significantly reduced, as compared with that by the standard reaction method.