Production of bacterial cellulose and enzyme from waste fiber sludge

Biotechnology for Biofuels

Adnan Cavka¹  Xiang Guo²  Shui-Jia Tang²  Sandra Winestrand¹  Leif J Jönsson¹  Feng Hong² 

[1] Department of Chemistry, Umeå University, Umeå, SE-901 87, Sweden

[2] Group of Microbiological Engineering and Industrial Biotechnology, College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai, 201620, China

关键词: Fiber sludge;    Trichoderma reesei;    Cellulase;    Enzyme production;    Gluconacetobacter xylinus;    Bacterial cellulose;   

Others  :  798146
DOI  :  10.1186/1754-6834-6-25

 received in 2012-09-05, accepted in 2013-02-14,  发布年份 2013

【 摘 要 】

Background

Bacterial cellulose (BC) is a highly crystalline and mechanically stable nanopolymer, which has excellent potential as a material in many novel applications, especially if it can be produced in large amounts from an inexpensive feedstock. Waste fiber sludge, a residue with little or no value, originates from pulp mills and lignocellulosic biorefineries. A high cellulose and low lignin content contributes to making the fiber sludge suitable for bioconversion, even without a thermochemical pretreatment step. In this study, the possibility to combine production of BC and hydrolytic enzymes from fiber sludge was investigated. The BC was characterized using field-emission scanning electron microscopy and X-ray diffraction analysis, and its mechanical properties were investigated.

Results

Bacterial cellulose and enzymes were produced through sequential fermentations with the bacterium Gluconacetobacter xylinus and the filamentous fungus Trichoderma reesei. Fiber sludges from sulfate (SAFS) and sulfite (SIFS) processes were hydrolyzed enzymatically without prior thermochemical pretreatment and the resulting hydrolysates were used for BC production. The highest volumetric yields of BC from SAFS and SIFS were 11 and 10 g/L (DW), respectively. The BC yield on initial sugar in hydrolysate-based medium reached 0.3 g/g after seven days of cultivation. The tensile strength of wet BC from hydrolysate medium was about 0.04 MPa compared to about 0.03 MPa for BC from a glucose-based reference medium, while the crystallinity was slightly lower for BC from hydrolysate cultures. The spent hydrolysates were used for production of cellulase with T. reesei. The cellulase activity (CMCase activity) in spent SAFS and SIFS hydrolysates reached 5.2 U/mL (87 nkat/mL), which was similar to the activity level obtained in a reference medium containing equal amounts of reducing sugar.

Conclusions

It was shown that waste fiber sludge is a suitable raw material for production of bacterial cellulose and enzymes through sequential fermentation. The concept studied offers efficient utilization of the various components in fiber sludge hydrolysates and affords a possibility to combine production of two high value-added products using residual streams from pulp mills and biorefineries. Cellulase produced in this manner could tentatively be used to hydrolyze fresh fiber sludge to obtain medium suitable for production of BC in the same biorefinery.

【 授权许可】

   
2013 Cavka et al.; licensee BioMed Central Ltd.

【 图 表 】

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