Biobleaching of wheat straw-rich-soda pulp by the application of alkalophilic and thermophilic mannanase from Streptomyces sp. PG-08-3

An alkalophilic and thermophilic mannanase from Streptomyces sp. PG-08-3 was applied to wheat straw-rich-soda pulp to check its bleaching potential. Optimum conditions for bio-bleaching of pulp were as follows: Mannanase 5 Ug-1 of pulp at pH 8.5 with temperature 55ºC that enhanced the brightness by 7.3% and reduced the kappa number by 24.6% within 4 h of incubation. Tear index (20%) and burst index (11.2%) were also improved by mannanase-treated pulp as compared to the untreated pulp. Treatment of chemically (CEH1H2) bleached pulp with enzyme showed significant effect on release of chromophores, hydrophobic and reducing compounds. Mannanase-prebleaching of raw pulp reduced the use of hypochlorite by 16% to achieve brightness of resultant hand sheets similar to the fully chemically bleached pulp. Scanning electron microscopy of wheat straw rich soda-pulp after treatment with denatured and active mannanase was performed. There was appearance of micro-fibers on the surface of pulp that was treated with active mannanase.Key words: Biobleaching, mannanase, wheat straw-rich-soda pulp

Anaerobic utilization of pectinous substrates at extremely haloalkaline conditions by Natranaerovirga pectinivora gen. nov., sp. nov., and Natranaerovirga hydrolytica sp. nov., isolated from hypersaline soda lakes

Anaerobic enrichments at pH 10, with pectin and polygalacturonates as substrates and inoculated with samples of sediments of hypersaline soda lakes from the Kulunda Steppe (Altai, Russia) demonstrated the potential for microbial pectin degradation up to soda-saturating conditions. The enrichments resulted in the isolation of six strains of obligately anaerobic fermentative bacteria, which represented a novel deep lineage within the order Clostridiales loosely associated with the family Lachnospiraceae. The isolates were rod-shaped and formed terminal round endospores. One of the striking features of the novel group is a very narrow substrate spectrum for growth, restricted to galacturonic acid and its polymers (e.g. pectin). Acetate and formate were the final fermentation products. Growth was possible in a pH range from 8 to 10.5, with an optimum at pH 9.5–10, and in a salinity range from 0.2 to 3.5 M Na+. On the basis of unique phenotypic properties and distinct phylogeny, the pectinolytic isolates are proposed to be assigned to a new genus Natranaerovirga with two species N. hydrolytica (APP2T=DSM24176T=UNIQEM U806T) and N. pectinivora (AP3T=DSM24629T=UNIQEM U805T)