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Thermophilic methane fermentation was a valid approach for handling the stillage eluted from ethanol fermentation of waste paper and kitchen waste. The wide organic loading rate (OLR) range (2-14 g VTS/(L d)) for stable performance and relatively high energy recovery efficiency (79.0%) were achieved, and OLR of 8 g VTS/(L d) was optimum for achievement of highest biogas evolution and VTS removal efficiency. Microbial community analysis revealed that hydrolysis of cellulose was the critical step for methane production from the stillage.

Metagenomics has emerged to isolate novel enzymes from the uncultured microbiota in the environment. In this study, the metagenomic data obtained from camel rumen was considered as the potential source of microbial xylanase enzymes with proper activity in extreme conditions. The metagenomic data were assembled and contigs were used for in-silico identification of candidate thermostable enzyme. A novel thermostable xylanase enzyme, named PersiXyn1, with 1146 bp full-length gene which encodes a 381 amino acid protein was identified. Using the DNA template extracted from camel rumen metagenomic samples, the candidate enzyme genes were cloned and expressed in proper E. coli strains. The phylogenetic analysis showed the evolutionary position of PersiXyn1 among the known thermostable xylanases. The results of the CD analysis and determining the secondary structure of the enzyme, confirmed the presence of a high percentage of β-sheets as an important characteristic of thermophilic xylanases. The PersiXyn1 was active at a broad range of pH (6–11) and temperature (25–90 °C). The optimum pH and temperature were 8 and 40 °C respectively, and the enzyme maintained 80% of its maximum activity in the pH 8 and temperature 40 °C for 1 h. The Scanning electron microscope (SEM) micrograph of enzyme treated pulp clearly showed that the effective use of enzymes in fiber separation may reduce the cost of carton paper production. The novelty of this enzyme lies in the fact that it is highly active and stable in a broad range of pH and temperature. This study highlights the potential importance of camel microbiome for discovering novel thermostable enzymes with applications in agriculture and industries.

A comparative study on the treatment of thermomechanical pulping (TMP) pressate was conducted under thermophilic (55 degrees C) and mesophilic (30 degrees C) temperatures to explore in-mill biological treatment, with the intention to operate under heat-efficient conditions. The experimental study involved sequencing batch reactors (SBRs) operated over 114 days. Receiving a total influent chemical oxygen demand (COD) of 3700-4100 mg L(-1), the COD removal efficiencies of 80-90% and 75-85% were achieved for the mesophilic and thermophilic SBRs, respectively, at a hydraulic retention time (HRT) of 12 and 24h. Excellent sludge settleability (sludge volume index100 mL g(-1) mixed liquor suspended solids) was obtained at both thermophilic and mesophilic SBRs. A higher level of effluent suspended solids was observed under thermophilic conditions. The results support the feasibility of applying thermophilic biological treatment of TMP pressate. The treated effluent has the potential for subsequent reuse as process water after polishing, thus addressing the long-standing desire to develop water system closure for the pulp and paper mill operation.

Xylanase is an enzyme in high demand for various industrial applications, such as those in the biofuel and pulp and paper fields. In this study, xylanase-producing microbes were isolated from the gut of the wood-feeding termite at 50°C. The isolated microbe produced thermostable xylanase that was active over a broad range of temperatures (40–90°C) and pH (3.5–9.5), with optimum activity (4,170 ± 23.5 U mg−1) at 60°C and pH 4.5. The enzyme was purified using a strong cation exchanger and gel filtration chromatography, revealing that the protein has a molecular mass of 205 kDa and calculated pI of 5.38. The half-life of xylanase was 6 h at 60°C and 2 h at 90°C. The isolated thermostable xylanase differed from other xylanases reported to date in terms of size, structure, and mode of action. The novelty of this enzyme lies in its high specific activity and stability at broad ranges of temperature and pH. These properties suggest that this enzyme could be utilized in bioethanol production as well as in the paper and pulp industry.

The aim of this work was to characterize the cultivable obligate anaerobic bacterial population in paper mill environments. A total of 177 anaerobically grown bacterial isolates were screened for aerotolerance, from which 67 obligate anaerobes were characterized by automated ribotyping and 41 were further identified by partial 16S rDNA sequencing. The mesophilic isolates indicated 11 different taxa (species) within the genus Clostridium and the thermophilic isolates four taxa within the genus Thermoanaerobacterium and one within Thermoanaerobacter (both formerly Clostridium). The most widespread mesophilic bacterium was closely related to C. magnum and occurred in three of four mills. One mill was contaminated with a novel mesophilic bacterium most closely related to C. thiosulfatireducens. The most common thermophile was T. thermosaccharolyticum, occurring in all four mills. The genetic relationships of the mill isolates to described species indicated that most of them are potential members of new species. On the basis of identical ribotypes clay could be identified to be the contamination source of thermophilic bacteria. Automated ribotyping can be a useful tool for the identification of clostridia as soon as comprehensive identification libraries are available.

Biofilms cause several problems in papermaking. This report describes a microbiological survey of colored biofilms in six paper and board machines, including two case studies of outbreaks of colored slimes in which the causative bacteria were found. A total of 95 pink-, red-, orange- or yellow-pigmented strains were isolated. Nearly all (99%) of the strains grew at 52 degrees C, 72% grew at 56 degrees C, but only 30% grew at 28 degrees C, indicating that most of the strains were moderately thermophilic. Biofilm formation potential and biocide susceptibility of the strains were analyzed with a microtiter plate assay. In the presence of 5 ppm of methylene bisthiocyanate or 2,2-dibromo-3-nitrilopropionamide in paper-machine water, 55 strains formed biofims. Moreover, 39 strains increased biofilm production by 5-753% in the presence of biocide, suggesting that biocide concentrations inhibitory to planktonic but not to surface-attached cells may actually promote biofouling. The cells may have inactivated a portion of the biocides, as the cell density in this assay was high, corresponding to the highest cell densities occurring in the circulating waters. Four groups of colored bacteria that were isolated from several mills were identified. Pink-pigmented Deinococcus geothermalis and red-pigmented Meiothermus silvanus occurred as common primary biofilm-formers in paper machines. This report is the first description of the involvement of Meiothermus species in red-slime formation in the paper industry. The third group of bacteria (putative new species related to Roseomonas) contained strains that were not biofilm formers, but which were commonly found in slimes of neutral or alkaline machines. The fourth group contained red-pigmented biofilm-forming strains representing a novel genus of alpha- Proteobacteria related to Rhodobacter. Many colored paper-machine bacteria are species previously known from microbial mats of hot springs. Some characteristics of the bacterial groups are described here in order to facilitate their recognition in future cases of colored-slime outbreaks in the paper industry.

A two-stage pilot-scale thermophilic aerobic suspended carrier biofilm process (SCBP) was set up for the on-site treatment of pulp and paper mill whitewater lining. The microbial diversity in this process was analyzed by length heterogeneity analysis of PCR-amplified 16S ribosomal DNA. The primer pair selected for PCR amplification was first evaluated by a computational analysis of fragment lengths in ten main phylogenetical eubacterial groups. The fragment contained the first third of the 16S rRNA gene, which was shown to vary naturally between 465 and 563 bp in length. The length heterogeneity analysis of polymerase chain reaction (LH-PCR) profile of the biomass attached to carrier elements was found to be diverse in both stages of the SCBP. During normal operating conditions, sequences belonging to beta-Proteobacteria, Cytophaga/Flexibacter/Bacteroides group and gamma-Proteobacteria were assigned to the most prominent LH-PCR peak. Samples from the suspended biomass consisted of completely different bacterial populations, which were, however, similar in the serial reactors. The pilot process experienced alkaline shocks, after which Bacillus-like sequences were detected in both the biofilm and suspended biomass. However, when the conditions were reversed, the normal microbial population in the biofilm recovered rapidly without further biomass inoculations. This study shows that LH-PCR is a valuable method for profiling microbial diversity and dynamics in industrial wastewater processes.