Co-metabolic Effect of Glucose on Methane Production and Phenanthrene Removal in an Enriched Phenanthrene-Degrading Consortium Under Methanogenesis

Anaerobic digestion is used to treat diverse waste classes, and polycyclic aromatic hydrocarbons (PAHs) are a class of refractory compounds that common in wastes treated using anaerobic digestion. In this study, a microbial consortium with the ability to degrade phenanthrene under methanogenesis was enriched from paddy soil to investigate the cometabolic effect of glucose on methane (CH4) production and phenanthrene (a representative PAH) degradation under methanogenic conditions. The addition of glucose enhanced the CH4 production rate (from 0.37 to 2.25mg⋅L−1⋅d−1) but had no influence on the degradation rate of phenanthrene. Moreover, glucose addition significantly decreased the microbial α-diversity (from 2.59 to 1.30) of the enriched consortium but showed no significant effect on the microbial community (R2=0.39, p=0.10), archaeal community (R2=0.48, p=0.10), or functional profile (R2=0.48, p=0.10). The relative abundance of genes involved in the degradation of aromatic compounds showed a decreasing tendency with the addition of glucose, whereas that of genes related to CH4 synthesis was not affected. Additionally, the abundance of genes related to the acetate pathway was the highest among the four types of CH4 synthesis pathways detected in the enriched consortium, which averagely accounted for 48.24% of the total CH4 synthesis pathway, indicating that the acetate pathway is dominant in this phenanthrene-degrading system during methanogenesis. Our results reveal that achieving an ideal effect is diffcult via co-metabolism in a single-stage digestion system of PAH under methanogenesis; thus, other anaerobic systems with higher PAH removal efficiency should be combined with methanogenic digestion, assembling a multistage pattern to enhance the PAH removal rate and CH4 production in anaerobic digestion.

Correlation between Metabolic Specialization and Codon Preference: Analysis of the Ligninolytic Genes from the White Rot Basidiomycete Ceriporiopsis Subvermispora as A Model System.

Background: Ceriporiopsis subvermispora is a white-rot fungus that displays a high specificity towards lignin mineralization when colonizing dead wood or lignocellulosic compounds. The lignocellulose degrading system from C. subvermispora is formed by genes that encode cellulose hydrolytic enzymes, manganese peroxidases, and laccases that catalyze the efficient depolymerization and mineralization of lignin in the presence of Mn3+ through the formation of lipoperoxides from unsaturated lipid acids. This highly specific lignin-degrading system is unique among white-rot fungi. Methods: In order to determine if this metabolic specialization has modified codon usage of the ligninolytic system, leading to an increased adaptation to the fungal translational machine, we analyzed the adaptation to host codon usage (CAI), tRNA pool (tAI, and AAtAI), codon pair bias (CPB) and the number of effective codons (Nc). These indexes were correlated with gene expression of C. subvermispora, as evaluated by microarray in the presence of two carbon sources, glucose and Aspen wood.Results: General gene expression of C. subvermispora was not correlated with the CAI, tAI, AAtAI, CBP or Nc indexes used to evaluate adaptation to codon bias or the tRNA pool, neither in the presence of glucose or Aspen wood. However, in media containing Aspen wood, the induction of expression of lignin-degrading genes showed a strong correlation with all the former indexes. Lignin-degrading genes, defined as genes whose expression increases at least two-fold in Aspen wood, showed significantly (p<0.001) higher values of CAI, AAtAI, CPB, tAI and lower values of Nc with respect to non-induced genes. Among ligninolytic genes, cellulose-binding proteins and manganese peroxidases presented the highest adaptation values. We also identified an expansion of genes encoding glycine and glutamic acid tRNAs.Conclusions: Our results suggest that the metabolic specialization to use wood as the sole carbon source has introduced a bias in the codon usage of genes involved in lignocellulose degradation. This bias reduces codon diversity and increases codon usage adaptation to the tRNA pool available in C. subvermispora. To our knowledge, this is the first study showing that codon usage is modified to improve the translation efficiency of a group of genes involved in a particular metabolic pathway.

Implementation and Evaluation of Steganography Based Online Voting System

Though there are online voting systems available, the authors propose a new and secure steganography based E2E (end-to-end) verifiable online voting system, to tackle the problems in voting process. This research implements a novel approach to online voting by combining visual cryptography with image steganography to enhance system security without degrading system usability and performance. The voting system will also include password hashed-based scheme and threshold decryption scheme. The software is developed on web-based Java EE with the integration of MySQL database server and Glassfish as its application server. The authors assume that the election server used and the election authorities are trustworthy. A questionnaire survey of 30 representative participants was done to collect data to measure the user acceptance of the software developed through usability testing and user acceptance testing.