Background： Bacterial cellulose (BC) is a nanostructured material with unique properties and wide applicability. In order to decrease the production cost of bacterial cellulose, lignocellulose-based media have considerable potential as alternative cost-effective feedstocks. However, pretreatment and enzymatic hydrolysis of lignocellulose to sugars also generate fermentation inhibitors. Detoxification of lignocellulosic hydrolysates is needed to achieve efficient production of BC. In this investigation, different methods for detoxification of spruce hydrolysate prior to production of BC were compared with respect to effects on potential inhibitors and fermentable sugars, sugar consumption, BC yield, and cell viability. The objectives were to identify efficient detoxification methods and to achieve a better understanding of the role played by different inhibitors in lignocellulosic hydrolysates. Results： In a first series of experiments, the detoxification methods investigated included treatments with activated charcoal, alkali [sodium hydroxide, calcium hydroxide (overliming), and ammonium hydroxide], anion and cation ion-exchange resins, and reducing agents (sodium sulfite and sodium dithionite). A second series of detoxification experiments included enzymatic treatments (laccase and peroxidase). The potential inhibitors studied included aliphatic acids, furan aldehydes, and phenolic compounds. The best effects in the first series of detoxification experiments were achieved with activated charcoal and anion exchanger. After detoxification with activated charcoal the BC yield was 8.2 g/L, while it was 7.5 g/L in a reference medium without inhibitors. Treatments with anion exchanger at pH 10 and pH 5.5 gave a BC yield of 7.9 g/L and 6.3 g/L, respectively. The first series of experiments suggested that there was a relationship between the BC yield and phenolic inhibitors. Therefore, the second series of detoxification experiments focused on treatments with phenol-oxidizing enzymes. The BC yield in the laccase-detoxified hydrolysate reached 5.0-5.5 g/L after 14 days cultivation, which demonstrated the important inhibitory role played by phenolic compounds. Conclusions： The investigation shows that detoxification methods that efficiently remove phenolics benefit bacterial growth and BC production. Negative effects of salts could not be excluded and the osmotolerance of Gluconacetobacter xylinus needs to be further investigated in the future. Combinations of detoxification methods that efficiently decrease the concentration of inhibitors remain as an interesting option. ___________________________________________________ http://www.microbialcellfactories.com/content/12/1/93 http://www.microbialcellfactories.com/content/pdf/1475-2859-12-93.pdf

草酸脱羧酶是一种含锰的酶，在白腐菌中广泛存在，少数低等真菌和细菌中也能产生。目前，至少十多种草酸脱羧酶得到了分离和纯化。该酶是一种氨基酸残基在379个左右的单体酶，一般都为酸性糖蛋白，含有2个锰离子，形成2个活性区域；表面一些氨基酸被不同程度地糖基化。晶体结构和其它一些波谱学研究解释了其空间结构和可能的电子传递机制。运用PCR技术和cDNA文库技术，越来越多的草酸脱羧酶基因被克隆。已研究的该酶基因中都含有17个左右的内含子，这些内含子在活性域位置上有比较高的保守性。一些特殊氨基酸序列的存在决定了该酶的表达形式为诱导型，菌株的基因调控序列中含有一段受草酸化合物作用的序列。该酶在一些酵母和植物等异源表达系统中有成功表达的报道。该酶的应用主要集中在以下几方面：造纸废水中的草酸盐降解；食品中的草酸降解；草酸生物检测（如临床诊断）等。

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. http://www.biotechnologyforbiofuels.com/content/6/1/25 http://www.biotechnologyforbiofuels.com/content/pdf/1754-6834-6-25.pdf

An ionic liquid [AMIM]Cl was used to pretreat wheat straw with an aim to remarkably improve enzymatic hydrolysis rate and yield of fermentable sugars. Some influence factors including dosage of straw, particle size of straw meal as well as pretreatment time and temperature were investigated. After optimization,the hydrolytic efficiency of regenerated straw increased obviously as compared to untreated materials, and the sugar yield of straw was 71.2% after pretreatment in [AMIM]Cl at 110 oC for 1.5 h with a 3 w/w% straw dosage, 3.6 times higher than that of untreated straw (19.6%). The reason behind the acceleration of enzymatic hydrolysis was discussed by the analysis of SEM, XRD and FTIR. The yield of bacterial cellulose obtained in straw hydrolysates was higher than that in glucose-based media. This may be due to the presence of other complex components in the hydrolysate that would enhance the formation of bacterial cellulose.