High level expression of a recombinant xylanase by Pichia pastoris NC38 in a 5 L fermenter and its efficiency in biobleaching of bagasse pulp

A genetically modified XynA gene from Thermomyces lanuginosus was expressed in Pichia pastoris under the control of GAP promoter. P. pastoris expressed greater levels of xylanase (160 IU ml(-1)) on BMGY medium without zeocin after 56 h. The xylanase production by recombinant P. pastoris was scaled up in a 5L fermenter containing 1% glycerol and the highest xylanase production of 139 IU ml(-1) was observed after 72 h. Further studies carried out in fermenter under controlled pH (5.5) yielded a maximum xylanase production of 177 IU ml(-1) after 72 h. The biobleaching efficacy of crude xylanase was also evaluated on bagasse pulp and a brightness of 47.4% was observed with 50 IU of crude xylanase used per gram of pulp, which was 2.1 points higher in brightness than the untreated samples. Reducing sugars (24.8 mg g(-1)) and UV absorbing lignin-derived compounds values were considerably higher with xylanase treated samples.     

Reproductive features of the Russian vole in laboratory breeding.

Reproductive features of newly bred Russian voles (Microtus rossiaemeridionalis) as a laboratory animal were studied. This species is a copulatory ovulator, and most couples copulated 6 to 16 h after pairing. The gestation period varied from 18 to 22 days (mean +/- SD: 20.6 +/- 0.9, n = 72), and the average litter size was 4.6 +/- 1.9 (n = 125). Compared with the litter size at the first parturition (3.6 +/- 1.6, n = 72), the litter size in the subsequent parturitions increased to 5.9 +/- 1.4 (n = 53). The animals exhibited postpartum estrus, and repeated pregnancy accompanied with suckling pups and parturition continuously in the laboratory condition unlike other vole species. In view of their complex stomach and good proliferation, the Russian voles were evaluated as a good laboratory animal, especially as a model animal for ruminant studies.     

Edibility of fresh and decomposing macrophytes to three species of freshwater invertebrate herbivores

The edibility of two endemic Australian macrophytes (Ottelia ovalifolia and Triglochin procera) to three species of herbivorous stream invertebrates (Triplectides ciuskus and Notalina fulva: (Trichoptera: Leptoceridae) and Potamopyrgus niger (Gastropods: Hydrobiidae)) was investigated. Each macrophyte species was offered to the test animals in 5 different conditions: fresh, boiled, and three conditions of decomposition. In 5 out of 6 feeding trials, consumption rates of animals were greatest on decomposed tissues. Boiling increased edibility of both plant species to Triplectides larvae and of Triglochin to Notalina larvae. Boiled tissue was consumed least by Potamopyrgus. Analysis of nitrogen, phosphorus, and calorific content of macrophyte tissue and some terrestrial plant materials known to be eaten by the animals suggested that nutritional enrichment of decomposed and boiled tissues was unlikely to explain their greater edibility. Instead, the loss of anti-gustatory compounds is implicated.