Isolation and identification of local Bacillus isolates for xylanase biosynthesis.

BACKGROUND AND OBJECTIVES: Bacillus species are attractive industrial organisms due to their rapid growth rates leading to a short fermentation cycle and for their capacity to secrete important enzymes and proteins such as xylanase into the extracellular medium. Considering the industrial importance of xylanase, in this current study, Bacillus spp. were isolated from different soils and were screened for their xylanase production. MATERIALS AND METHODS: Bacillus isolates used in this study were obtained from a national screening program carried out during 2006-2007 in which soil samples that covered areas throughout the interior of Syria were collected. The prepared inoculum from each of Bacillus isolates was aliquoted onto xylan agar plates, incubated at 30°C for 72 h and screened for xylanase synthesis. RESULTS: Xylanolytic isolates were selected depending on the clear zones of xylan hydrolysis. Fifteen isolates having the highest clearing zone were determined and grown in a solid state fermentation. Of the 15 isolates, three bacilli namely SY30A, SY185C and SY190E that showed maximum xylanase production, were identified using the 16S rDNA sequencing method. According to 16S rDNA gene sequence data, the closest phylogenetic neighbor for SY30A was Bacillus pumilus and for SY185C and SY190E isolates was Bacillus subtilis. Optimal pH and temperature for xylanase activity was 7.0 and 55ºC for SY30A and 6.0 and 60ºC for SY185C and SY190E, respectively. Under these conditions, the following activities were found to be around 1157 ± 58, 916 ± 46 and 794 ± 39 (U/g) for SY30A, SY185C and SY190E, respectivly. CONCLUSIONS: Selected local Bacillus isolates were found to be a potential source of xylanase which was proven to be quite suitable for multiple biotechnological applications. These isolates might after extensive optimization steps be an alternative to commercially available strains.

Extracellular xylanase production by Fusarium species in solid state fermentation.

Fusarium sp. has been shown to be a promising organism for enhanced production of xylanases. In the present study, xylanase production by 21 Fusarium sp. isolates (8 Fusarium culmorum, 4 Fusarium solani, 6 Fusarium verticillioides and 3 Fusarium equiseti) was evaluated under solid state fermentation (SSF). The fungal isolate Fusarium solani SYRN7 was the best xylanase producer among the tested isolates. The effects of some agriculture wastes (like wheat straw, wheat bran, beet pulp and cotton seed cake) and incubation period on xylanase production by F. solani were optimized. High xylanase production (1465.8 U/g) was observed in wheat bran after 96 h of incubation. Optimum pH and temperature for xylanase activity were found to be 5 and 50 degrees C, respectively.

Influence of agitation speeds and aeration rates on the Xylanase activity of Aspergillus niger SS7

In this study, the effect of agitation and aeration rates on xylanase activity of Aspergillus niger SS7 in 3-litre stirred tank bioreactor was investigated. The agitation rates tested were 100, 200 and 300 rpm at each airflow rates of 0.5, 1.0 and 1.5 vvm. The maximum xylanase activity in mono- agitator system was at the agitation speed of 200 rpm and aeration rate of 1.0 vvm. In bi-agitator system, at low agitation speed (100 rpm), the xylanase activity was enhanced by 13 percent compared to mono- agitator system for an aeration rate of 1.0 vvm. Xylanase productivity in continuous culture was higher by approximately 3.5 times than in batch culture.

Isolation and identification of two new fungal strains for xylanase production.

Fungi are well known for their ability to excrete enzymes into the environment. The aim of this work was to evaluate xylanase production by fungi isolated from soil. One hundred and thirty-six fungal isolates were screened for xylanase production. Two xylanase producing isolates, FSS117 and FSS129, were identified on the basis of analyses of 5,8S gene sequencing. The closest phylogenetic neighbors according to 5,8S gene sequence data for the two isolates were Aspergillus tubingensis and Aspergillus terreus, respectively. When birchwood xylan or corn cob hulls was used as a substrate for 5 days under submerged culture cultivation, xylanase production from A. terreus FSS129 was 113 and 174 IU ml(-1), respectively. The pH and temperature for optimum xylanase activity were 8 and 65 degrees C.

Isolation and identification of a new fungal strain for amylase biosynthesis.

Fungi are well known for their ability to excrete enzymes into the environment. The fungal isolate FSS60 was the best amylase producer among one hundred and thirty-six isolates obtained from Syrian soils and tested for amylase production. According to the sequence of the internal transcribed spacer (ITS) rDNA gene, the isolate was identified as Aspergillus flavus. Optimal initial pH for amylase production was found to be 9.0. The enzyme was optimally active at 50 degrees C and pH 5.0.

Xylanase production by a newly isolated Aspergillus niger SS7 in submerged culture.

Xylanase production by a newly isolated Aspergillus niger SS7 was studied in submerged culture. The optimum initial pH for xylanase production was found to be 7.0. Different agricultural and industrial wastes were evaluated for their ability to induce xylanase production by this isolate. The best xylanase production (293.82 IU/ml) was recorded at 3% (w/v) corn cob hulls after 120 h of incubation. The Aspergillus niger SS7 isolate grown in a simple medium, proved to be a promising microorganism for xylanase production.

Improvement of xylanase production by Cochliobolus sativus in solid state fermentation / Melhoramento da produção de xilanase por Cochliobolus sativus por fermentação em estado sólido

The xylanase production by Cochliobolus sativus strain Cs6 was improved under solid state fermentation (SSF). High xylanase activity (1079 U/g) was obtained when wheat straw was used after 8 days of incubation. Combinations of sodium nitrate with peptone or yeast extract resulted in an increased xylanase production (1543 and 1483 U/g, respectively). The Cs6 strain grown in SSF in a simple medium, proved to be a promising microorganism for xylanase production.

A produção de xilanase por Cochliobolus sativus cepa Cs6 SATIVUS por fermentação em estado sólido (SSF) foi melhorada. Com o emprego de palha de trigo, obteve-se elevada atividade de xilanase (1079 U/g) após 8 dias de incubação. Combinações de nitrato de sódio com peptona ou extrato de levedura aumentaram a produção de xilanase (1543 e 1483 U/g, respectivamente). Comprovou-se que a cepa Cs6, cultivada em SSF em meio simples, é um microrganismo promissor para produção de xilanase.

Polymorphism in the ITS region of ribosomal DNA of Cochliobolus sativus isolates differing in xylanase production.

The restriction of PCR-amplified internal transcribed spacers (ITS) ofribosomal DNA was used to confirm the genetic variation among 22 isolates of Cochliobolus sativus differing in their xylanase production. Results show a high level of diversity of ITS-RFLP markers among the isolates. The molecular parameter used showed that C. sativus isolates reside in three phylogenetic groups. There was observed the resolution between clustering of isolates and their xylanase production level.

Improvement of xylanase production by Cochliobolus sativus in solid state fermentation.

The xylanase production by Cochliobolus sativus strain Cs6 was improved under solid state fermentation (SSF). High xylanase activity (1079 U/g) was obtained when wheat straw was used after 8 days of incubation. Combinations of sodium nitrate with peptone or yeast extract resulted in an increased xylanase production (1543 and 1483 U/g, respectively). The Cs6 strain grown in SSF in a simple medium, proved to be a promising microorganism for xylanase production.

RAPD technique is a useful tool to distinguish Penicillium species.

Random amplified polymorphic DNA (RAPD) analysis was used to evaluate genetic diversity among 13 soil Penicillium strains originating from widely dispersed areas. Twenty one of the 34 synthetic random primers were found to identify polymorphism in amplification products. The results show a high level of diversity of RAPD markers among the strains. All the strains could be identified by their characteristic amplification profile, using selected random primers. This suggests that RAPD analysis is a useful and reliable assay for characterizing the species of Penicillium genus.

Xylanase production by Penicillium canescens 10-10c in solid-state fermentation.

Filamentous fungi have been widely used to produce hydrolytic enzymes for industrial applications, including xylanases, whose levels in fungi are generally much higher than those in yeast and bacteria. We evaluated the influence of carbon sources, nitrogen sources, and moisture content on xylanase production by Penicillium canescens 10-10c in solid-state fermentation. Among agricultural wastes tested (wheat bran, untreated wheat straw, treated wheat straw, beet pulp, and soja meal), untreated wheat straw gave the highest production of xylanase. Optimal initial moisture content for xylanase production was 83%. The addition of 0.4 g of xylan or easily metabolizable sugar, such as glucose and xylose, at a concentration of 2 % to wheat straw enhanced xylanase production. In solid-state fermentation, even at high concentrations of glucose or xylose (10%), catabolic repression was minimized compared to the effect observed in liquid culture. Yeast extract was the best nitrogen source among the nitrogen sources investigated: peptone, ammonium nitrate, sodium nitrate, ammonium chloride, and ammonium sulfate. A combination of yeast extract and peptone as nitrogen sources led to the best xylanase production.

Influence of a new axial impeller on K(L)a and xylanase production by Penicillium canescens 10-10c.

The effects of a new axial impeller (HTPG4) on oxygen volumetric transfer coefficient, K(L)a, and xylanase production by Penicillium canescens 10-10c were studied and compared for dual-impeller systems, one with one DT4 impeller below and one HTPG4 above (DT4-HTPG4) and one with two DT4 (DT4-DT4) impellers, in a 5-L bioreactor. The volumetric coefficient of oxygen transfer was measured in culture medium using a gassing-out method at different gassing rates and agitation speeds. We observed that the DT4-HTPG4 combination provided better K(L)a performance than the DT4-DT4 combination. The two combinations were also tested for their influence on xylanase production by a filamentous microorganism; P. canescens 10-10c. These experiments demonstrated that the DT4-HTPG4 combination impeller enhanced enzyme production up to 23% compared with the DT4-DT4 combination at an aeration rate of 1 vvm and an agitation speed of 600 rpm. The main cause for this difference is thought to be a higher shear stress generated by the DT4-DT4 combination, which damages the mycelium of P. canescens and decreases xylanase production.