Improving enzymatic digestibility of wheat straw pretreated by a cellulase-free xylanase-secreting Pseudomonas boreopolis G22 with simultaneous production of bioflocculants

Abstract

BackgroundXylan removal by bacterial pretreatments has been confirmed to increase the digestibility of biomass. Here, an effective xylan removal technique has been developed to enhance the digestibility of wheat straw and simultaneously produce bioflocculants by a cellulase-free xylanase-secreting strain, Pseudomonas boreopolis G22.ResultsThe results indicated that P. boreopolis G22 is an alkaliphilic strain which can secrete abundant amounts of xylanase. This xylanase had activity levels of 2.67–1.75 U mL−1 after an incubation period of 5–25 days. The xylanase showed peak activity levels at pH 8.6, and retained more than 85% relative activity in the pH range of 7.2–9.8. After 15 days of cultivation, the hemicellulose contents of the wheat straw were significantly decreased by 32.5%, while its cellulose contents were increased by 27.3%, compared to that of the control. The maximum reducing sugars released from the 15-day-pretreated wheat straw were 1.8-fold higher than that of the untreated wheat straw, under optimal enzymatic hydrolysis conditions. In addition, a maximum bioflocculant yield of 2.08 g L−1 was extracted from the fermentation broth after 15 days of incubation. The aforementioned bioflocculants could be used to efficiently decolorize a dye solution.ConclusionsThe results indicate that the cellulase-free xylanase-secreting P. boreopolis G22 may be a potential strain for wheat straw pretreatments. The strain G22 does not only enhance the enzymatic digestibility of wheat straw, but also simultaneously produces a number of bioflocculants that can be used for various industrial applications.

Elevated Atmospheric CO2 Modifies Mostly the Metabolic Active Rhizosphere Soil Microbiome in the Giessen FACE Experiment

“…4, S2) that have been previously reported to degrade lignocellulose materials. Pseudomonas boreopolis produces a cellulase-free xylanase with a high activity of hemicellulose degradation [85]. Maki et al [86] reported that Bacillus strain (55S5) and a Pseudomonas strain (AS1) displayed high potential for lignocellulose decomposition due to a variety of cellulase and xylanase activities.…”

Dilution-to-Stimulation/Extinction Method: a Combination Enrichment Strategy To Develop a Minimal and Versatile Lignocellulolytic Bacterial Consortium

“…Soil-derived Pseudomonas species have been recognized as powerful ligninolytic microbes ( 34 , 56 , 57 ). In addition, they can secrete endoxylanases during wheat straw degradation processes ( 58 , 59 ). Moreover, a strong correlation of cellulose degradation with the presence of Paenibacillus species has been reported in a synthetic LMC ( 19 ).…”

Silage quality and biogas production from Spartina pectinata L. fermented with a novel xylan-degrading strain of Lactobacillus buchneri M B/00077

“…Spartina pectinata L., as well as various agricultural residues and other herbaceous plants, could become an important feedstock for the production of biofuels 1 . Lignocellulose biomass is a commonly available and renewable energy source, and 55-75% of it consists of polymers (cellulose, hemicellulose, lignin) by dry weight and can be used for ethanol, as well as for biogas production during the anaerobic digestion (AD) process 2 . However, the main drawback of the lignocellulosic biomass is its structural heterogeneity and complexity causing the native biomass resistance to enzymatic hydrolysis creating thereby an obstacle for the AD process and finally, limiting biogas production.…”

“…However, the main drawback of the lignocellulosic biomass is its structural heterogeneity and complexity causing the native biomass resistance to enzymatic hydrolysis creating thereby an obstacle for the AD process and finally, limiting biogas production. Hemicelluloses, especially xylan, if coated with crystalline cellulose restricts access to the cellulose microfibrils, making them water insoluble and recalcitrant to biodegradation 2,3 . Moreover, a high content of barely degradable fibre fractions in biomass intended for the production of gaseous biofuels limits the yield of methane produced 4 .…”

“…The biological pretreatment of lignocellulose biomass using microorganisms has been mostly associated with the action of fungi owing to their enzymatic capabilities [14][15][16] . However, microorganisms having xylanolytic activity are also found among various bacteria 2,3 . For instance Zerva et al 17 isolated waste xylanolytic microbial strains from orange-juice processing, among which Pseudomonas psychrotolerans and P. oryzihabitans showed the highest extracellular endo-1,4-β-xylanase activity with 280 U/mg protein.…”