Production of xylanase by immobilized Trichoderma reesei SAF3 in Ca-alginate beads

Carbon nanomaterial properties help to enhance xylanase production from recombinant Kluyveromyces lactis through a cell immobilization method

Carbon nanomaterials, due to their catalytic activity and high surface area, have potential as cell immobilization supports to increase the production of xylanase. Recombinant Kluyveromyces lactis used for xylanase production was integrated into a polymeric gel network with carbon nanomaterials. Carbon nanomaterials were pretreated before cell immobilization with hydrochloric acid (HCl) treatment and glutaraldehyde (GA) crosslinking, which contributes to cell immobilization performance. Carbon nanotubes (CNTs) and graphene oxide (GO) were further screened using a Plackett-Burman experimental design. Cell loading and agar concentration were the most important factors in xylanase production with low cell leakage. Under optimized conditions, xylanase production was increased by more than 400% compared to free cells. Immobilized cell material containing such high cell densities may exhibit new and unexplored beneficial properties because the cells comprise a large fraction of the component. The use of carbon nanomaterials as a cell immobilization support along with the entrapment method successfully enhances the production of xylanase, providing a new route to improved bioprocessing, particularly for the production of enzymes. KEY POINTS: • Carbon nanomaterials (CNTs, GO) have potential as cell immobilization supports. • Entrapment in a polymeric gel network provides space for xylanase production. • Plackett-Burman design screen for the most important factor for cell immobilization.

Optimization of the Cellulase Free Xylanase Production by Immobilized Bacillus Pumilus

Background

The extracellular xylanase secreted by microorganisms is a hydrolytic enzyme, which arbitrarily cleaves the β-1, 4 backbone of the polysaccharide xylan; an enzyme used in the food processing, bio-pulping and bio-bleaching. The commercial production of the xylanase is limited because of a higher cost involvement, which can be overcome by the cost-effective production of the xylanase through immobilization of the microbial cell by the non-toxic substances.

Objectives

In this work, the optimization of the extra-cellular cellulase free xylanase production by the immobilized cell of the Bacillus pumilus IMAU80221 strain using Ca-alginate beads along with standardization of the various parameters for a higher xylanase production were studied.

Materials and Methods

Following to sterilization, the Na-alginate solution was mixed with the bacterial suspension of the Bacillus pumilus IMAU80221 and was added drop by drop into the 1 M calcium chloride solution for 1 h for obtaining a uniform sized polymeric bead of the Ca-alginate. For xylanase production, the Ca-alginate beads were then transferred into 100 mL Erlenmeyer flasks with 20 mL of the culture medium containing (w/v) 0.02% NaCl, 0.02% MgSO₄, 0.04% (KH₄)₂PO₄, 0.1% peptone, and 0.5% xylan and incubated at 34 °C in an incubator shaker (150 rpm) for 24 h. The resultant supernatant (crude enzyme) was used for enzyme assay.

Results

The maximum xylanase production by the free cell (1.9 U.mL^-1.min^-1) was recorded at 48 h which was 40.5% lower than the xylanase production by the immobilized cell (2.67 U.mL^-1.min^-1) at the same time. The beads containing the immobilized cells could be reused up to eight fermentation cycles for xylanase production and retained 83.5% of the productivity at the fourth cycle. The entrapped cells were stable after six months of storage at 4 °C and retained 68% of the xylanase productivity.

Conclusion

Cellulase free xylanase production from the immobilized Bacillus pumilus IMAU80221 was optimized. The xylanase production by the immobilized cells of Bacillus pumilus was higher by 40.5 and 132.6 % over the free cells respectively after 48 and 72 h of the incubation.

Calcium alginate matrix increases the stability and recycling capability of immobilized endo-β-1,4-xylanase from Geobacillus stearothermophilus KIBGE-IB29

Exploration of microbial pool from extremely diversified ecosystem is significantly important for various industrial applications. Bacterial communities from extreme habitats including volcanic vents, hot springs, and industrial sectors are eagerly explored for the isolation of thermophiles. Geobacillus stearothermophilus KIBGE-IB29, isolated from blast furnace site of a steel processing industry, is capable of producing thermostable endo-β-1,4-xylanase. In the current study, this enzyme was immobilized within calcium alginate beads using entrapment technique. Amalgamation of sodium alginate (40.0 gL(-1)) and calcium chloride (0.4 M) was used for the formation of immobilized beads. It was observed that temperature (50 °C) and pH (7.0) optima of immobilized enzyme remained same, but enzyme-substrate reaction time increased from 5.0 to 30.0 min as compared to free enzyme. Diffusion limit of high molecular weight xylan (corncob) caused a decline in V max of immobilized enzyme from 4773 to 203.7 U min(-1), whereas K m value increased from 0.5074 to 0.5722 mg ml(-1) with reference to free enzyme. Immobilized endo-β-1,4-xylanase showed its stability even at high temperatures as compared to free enzyme and retained 18 and 9 % residual activity at 70 and 80 °C, respectively. Immobilized enzyme also exhibited sufficient recycling efficiency up to five reaction cycles which indicated that this enzyme can be a plausible candidate in paper and pulp industry.

Uncovering the cultivable microbial diversity of costa rican beetles and its ability to break down plant cell wall components

Coleopterans are the most diverse insect order described to date. These organisms have acquired an array of survival mechanisms through their evolution, including highly efficient digestive systems. Therefore, the coleopteran intestinal microbiota constitutes an important source of novel plant cell wall-degrading enzymes with potential biotechnological applications. We isolated and described the cultivable fungi, actinomycetes and aerobic eubacteria associated with the gut of larvae and adults from six different beetle families colonizing decomposing logs in protected Costa Rican ecosystems. We obtained 611 isolates and performed phylogenetic analyses using the ITS region (fungi) and 16S rDNA (bacteria). The majority of fungal isolates belonged to the order Hypocreales (26% of 169 total), while the majority of actinomycetes belonged to the genus Streptomyces (86% of 241 total). Finally, we isolated 201 bacteria spanning 19 different families belonging into four phyla: Firmicutes, α, β and γ-proteobacteria. Subsequently, we focused on microbes isolated from Passalid beetles to test their ability to degrade plant cell wall polymers. Highest scores in these assays were achieved by a fungal isolate (Anthostomella sp.), two Streptomyces and one Bacillus bacterial isolates. Our study demonstrates that Costa Rican beetles harbor several types of cultivable microbes, some of which may be involved in symbiotic relationships that enable the insect to digest complex polymers such as lignocellulose.

Enhanced production of alkaline thermostable keratinolytic protease from calcium alginate immobilized cells of thermoalkalophilic Bacillus halodurans JB 99 exhibiting dehairing activity

The thermoalkalophilic Bacillus halodurans JB 99 cells known for production of novel thermostable alkaline keratinolytic protease were immobilized in calcium alginate matrix. Batch and repeated batch cultivation using calcium alginate immobilized cells were studied for alkaline protease production in submerged fermentation. Immobilized cells with 2.5% alginate and 350 beads/flask of initial cell loading showed enhanced production of alkaline protease by 23.2% (5,275 ± 39.4 U/ml) as compared to free cells (4,280 ± 35.4 U/ml) after 24 h. In the semicontinuous mode of cultivation, immobilized cells under optimized conditions produced an appreciable level of alkaline protease in up to nine cycles and reached a maximal value of 5,975 U/ml after the seventh cycle. The enzyme produced from immobilized cells efficiently degraded chicken feathers in the presence of a reducing agent which can help the poultry industry in the management of keratin-rich waste and obtaining value-added products.