Decolourisation of chemically different dyes by enzymes from spent compost of Pleurotus sajor-caju and their kinetics

A total of eight dyes from the triphenylmethane, azo and  polymeric/heterocyclic dye group were decolourized by enzyme cocktail extracted from five month old spent compost of Pleurotus sajor-cajuwith lignin peroxidase as the main enzyme. The percentage of decolourisation for tryphan blue, amido black, remazol brilliant blue R (RBBR) and bromophenol blue ranged between 80 - 90% after 4 hreaction. However, the percentage of decolourisation for crystal violet, methyl green and congo red was lower than the other dyes from the same dye group with only 60 - 65% after 12 h. Methylene blue exhibited the least decolourisation with only 43% after 24 h indicating that this dye is a poor substrate for the enzyme. The rate of decolourisation for crystal violet, tryphan blue, amido black, congo red and RBBR dyes by enzymes from spent mushroom compost (SMC) were also calculated. The rate ofdecolourisation for all the dyes was positively affected by the initial dye concentration, pH between 4.0 - 4.5 and temperature range of 30 - 35°C. The optimum concentration of veratryl alcohol as redox mediator was between 0 - 2 mM for all the dyes except for RBBR. The optimum veratryl alcohol concentration for RBBR was 4 mM. Based on the effect of hydrogen peroxide on the rate of decolourisation of each dye, the dyes could be divided into two groups. From the results of the present study, it could be concluded that the enzymes extracted from the spent compost of P. sajor-caju offers an economical advantage of obtaining industrially important enzymes, which have potential in the bioremediation of synthetic dyes. Furthermore, the utilization of spent compost for the extraction ofenzymes can also offer a possible solution for the problem posed due to the disposal of large amounts of spent mushroom compost

Revealing the biotechnological potential of Delftia sp. JD2 by a genomic approach

Delftia sp. JD2 is a chromium-resistant bacterium that reduces Cr(VI) to Cr(III), accumulates Pb(II), produces the phytohormone indole-3-acetic acid and siderophores, and increases the plant growth performance of rhizobia in co-inoculation experiments. We aimed to analyze the biotechnological potential of JD2 using a genomic approach. JD2 has a genome of 6.76Mb, with 6,051 predicted protein coding sequences and 93 RNA genes (tRNA and rRNA). The indole-acetamide pathway was identified as responsible for the synthesis of indole-3-acetic acid. The genetic information involved in chromium resistance (the gene cluster, chrBACF,) was found. At least 40 putative genes encoding for TonB-dependent receptors, probably involved in the utilization of siderophores and biopolymers, and genes for the synthesis, maturation, exportation and uptake of pyoverdine, and acquisition of Fe-pyochelin and Fe-enterobactin were also identified. The information also suggests that JD2 produce polyhydroxybutyrate, a carbon reserve polymer commonly used for manufacturing petrochemical free bioplastics. In addition, JD2 may degrade lignin-derived aromatic compounds to 2-pyrone-4,6-dicarboxylate, a molecule used in the bio-based polymer industry. Finally, a comparative genomic analysis of JD2, Delftia sp. Cs1-4 and Delftia acidovorans SPH-1 is also discussed. The present work provides insights into the physiology and genetics of a microorganism with many potential uses in biotechnology