The recovery and bioproperties of a xylanolytic multi-enzyme complex from Tepidimicrobium xylanilyticum BT14

A novel amylolytic/xylanolytic/cellulolytic multienzyme complex from Clostridium manihotivorum that hydrolyzes polysaccharides in cassava pulp

Some anaerobic bacteria, particularly Clostridium species, produce extracellular cellulolytic and xylanolytic enzymes as multienzyme complexes (MECs). However, an amylolytic/xylanolytic/cellulolytic multienzyme complex (AXC-MEC) from anaerobic bacteria is rarely found. In this work, the glycoprotein AXC-MEC, composed of subunits of amylolytic, xylanolytic, and cellulolytic enzymes, was isolated from crude extracellular enzyme of the mesophilic anaerobic bacterium Clostridium manihotivorum CT4, grown on cassava pulp, using a milled cassava pulp column and Sephacryl S-500 gel filtration chromatography. The isolated AXC-MEC showed a single band upon native-polyacrylamide gel electrophoresis (native-PAGE). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed at least eight protein bands of the multienzyme complex which predominantly exhibited amylolytic enzyme activity, followed by xylanolytic and cellulolytic enzyme activities. The AXC-MEC is highly capable of degrading starch and non-starch polysaccharides present in cassava pulp into glucose and oligosaccharides, without conventional pretreatment. Base on the genomic analysis of C. manihotivorum CT4, we found no evidence of the known structural components of the well-known multienzyme complexes from Clostridium species, cellulosomes such as scaffoldin, cohesin, and dockerin, indicating that AXC-MEC from strain CT4 exhibit a different manner of assembly from the cellulosomes. These results suggest that AXC-MEC from C. manihotivorum CT4 is a new MEC capable of hydrolyzing cassava pulp into value-added products, which will benefit the starch industry. KEY POINTS: • Glycoprotein AXC-MEC was first reported in Clostridium manihotivorum. • Unlike cellulosomes, AXC-MEC consists of amylase, xylanase, and cellulase. • Glucose and oligosaccharides were hydrolysis products from cassava pulp by AXC-MEC.

Structural and metabolic adaptation of cellulolytic microcosm in co-digested Napier grass-swine manure and its application in enhancing thermophilic biogas production

Biogas production from cellulosic wastes has received increasing attention. However, its efficiency is limited by the recalcitrant nature of plant cell wall materials. In this study, an active and structurally stable lignocellulolytic microcosm (PLMC) was isolated from seed culture in sugarcane bagasse compost by successive enrichment on Napier grass supplemented with swine manure, which is a mixture of highly fibrous co-digested waste under septic conditions. Tagged 16S rRNA gene sequencing on an Ion PGM platform revealed the adaptive merging of microorganisms in the co-digested substrates resulting in a stable symbiotic consortium comprising anaerobic cellulolytic clostridia stably co-existing with facultative (hemi)cellulolytic bacteria in the background of native microflora in the substrates. Ethanoligenens, Tepidimicrobium, Clostridium, Coprococcus, and Ruminococcus were the most predominant taxonomic groups comprising 72.82% of the total community. The remarkable enrichment of catabolic genes encoding for endo-cellulases and hemicellulases, both of which are key accessory enzymes in PLMC, was predicted by PICRUSt. PLMC was capable of degrading 43.6% g VS and 36.8% g VSS of the co-digested substrates within 7 days at 55 °C. Inoculation of the microcosm to batch thermophilic anaerobic digestion containing both substrates led to a 36.6% increase in methane yield along with an increase in cellulose removal efficiency. This study demonstrated structural and metabolic adaptation of the cellulolytic microcosms isolated in the background of native microflora from the co-digested wastes and its potent application in the enhancement of anaerobic digestion efficiency.

Structurally and functionally stable symbiotic cellulolytic consortium was established for enhancing the methane production from Napier grass co-digested with swine manure.