Sodium dodecyl sulfate improves the treatment of waste paper with rumen fluid at lower concentration but decreases at higher condition

Abstract

Rumen fluid has been applied to lignocellulosic biomass digest for methane production, and various feed supplements have been shown to improve ruminant digestion of lignocellulosic biomass. Therefore, we investigated the effects of sodium dodecyl sulfate (SDS) on the pretreatment of lignocellulosic biomass with rumen fluid and subsequent methane fermentation. SDS was mixed with rumen fluid at concentrations of 0.1, 0.2, 0.4, and 0.8 g/L. After SDS addition, the waste paper was pretreated with rumen fluid at 37 °C for 6 h. SDS addition decreased the number of surviving rumen ciliates after pretreatment. SDS addition increased the dissolved chemical oxygen demand during pretreatment; however, SDS addition did not increase the volatile fatty acid concentration. After pretreatment, batch methane fermentation of pretreated waste paper was performed at 35 °C for 45 days. SDS addition at 0.1 and 0.2 g/L shortened the waste paper digestion time and enhanced methane gas production compared to the control. By contrast, SDS addition at 0.4 and 0.8 g/L remarkably inhibited methane production from waste paper. These findings suggest that low concentrations of SDS can improve the efficiency of lignocellulosic biomass pretreatment with rumen fluid, and can enhance methane production from waste paper.

Shifts in xylanases and the microbial community associated with xylan biodegradation during treatment with rumen fluid

“…Thus, we speculate that Lactobacillus , Bifidobacterium , and Atopobium utilized xylan metabolites (i.e., xylooligosaccharides and xylose) and produced VFAs, especially lactic acid, after 24 h. The relative abundances of protozoal and fungal genera decreased during treatment. We previously reported that the relative abundances of protozoal and fungal genera significantly decreased during the treatment of carboxymethyl cellulose with rumen fluid for 48 h (Takizawa et al ., 2020a,b,c), which was consistent with the present results. Entodinium caudatum , Entodinium exiguum , Epidinium caudatum , and Ophryoscolex purkynjei decrease in abundance when the pH decreases below 5.4, whereas they maintain their levels around pH 5.8 (Dehority, 2005).…”

“…The dried pellets were solubilized in 1 ml of 2× sample buffer comprising 20% ( v / v ) glycerol, 4% ( w / v ) SDS, 0.01% ( w / v ) bromophenol blue, 0.125 M Tris‐HCl (pH 7.4), 10% ( v / v ) 2‐mercaptoethanol, 2 mM phenylmethylsulfonyl fluoride, and 1× proteinase inhibitor (Sigma‐Aldrich). SDS‐PAGE and zymography were conducted according to a previous study (Takizawa et al ., 2020a,b,c), with some modifications. Briefly, the supernatants were heated at 70°C for 20 min and immediately cooled on ice.…”

“…DNA extraction and metagenomic sequencing were carried out as previously described (Takizawa et al ., 2020a,b,c). Briefly, total DNA was extracted from 2 ml of rumen fluid using the FastDNA SPIN Kit for Soil (MP Biomedicals) according to the manufacturer’s instructions.…”

“…This pretreatment has been shown to improve methane gas production from rice straw (Zhang et al ., 2016), paper sludge (Takizawa et al ., 2018), and rapeseed (Baba et al ., 2017, 2019) by 1.5–3.4 times. Furthermore, low sodium dodecyl sulfate concentrations improve the efficiency of pretreatment with rumen fluid, enhancing methane production from waste paper (Takizawa et al ., 2020a,b,c).…”

“…Knowledge of the fibrolytic enzymes of ruminal microorganisms is vital for improving the biodegradation efficiency of lignocellulosic biomass during treatment with rumen fluid. We previously reported endoglucanase activity and the responsible microorganisms (Takizawa et al ., 2020a,b,c); however, hemicellulase activity has not yet been clarified. Xylan is the main component of hemicellulose, and the hydrolysis of xylan polymers is one of the rate‐limiting steps in anaerobic degradation of lignocellulosic biomass.…”