Assessment of the structural factors controlling the enzymatic saccharification of rice straw cellulose

In this study, the structural factors controlling the enzymatic saccharification of rice straw cellulose were examined by preparing structure-modified rice straw samples such as dewaxed, alkali-treated, oxidized, and swollen rice straw. It was found that the initial enzymatic saccharification rate of the various structure-modified samples was largely controlled by the initial cellulose surface area of the cellulose unit. Although the presence of lignin limited the cellulose surface area, there was no strong relationship between the lignin content and the initial reaction. On the other hand, the long-term enzymatic saccharification of rice straw cellulose highly depended on the lignin removal rate (lignin content). It was also found that silica is not a crucial factor in controlling the enzymatic saccharification.     

Comparison of steam-alkali-chemical and microwave-alkali pretreatment for enhancing the enzymatic saccharification of oil palm trunk

This paper demonstrates two different pretreatment protocols for oil palm trunks (OPT); steam-alkali-chemical (SAC) and microwave-alkali (Mw-A) method. The composition, morphology, structure and crystallinity of OPT before and after pretreatment were analyzed. The effectiveness of the pretreated methods was investigated by performing enzymatic saccharification on the OPT. The physiochemical factors namely: enzyme ratio (cellulase to β-glucosidase), pH, temperature and substrate loading (w/v) on enzymatic saccharification were also investigated. The pre-determined optimal conditions were then used for further enzymatic hydrolysis of raw and pretreated OPT substrates. The results revealed a huge degree of reduction in lignin, up to 89% for SAC treated OPT and at least 15% for Mw-A treated OPT sample as compared to untreated ones. High glucose accumulation (79.4%) was obtained after 72 h saccharification for both pretreated OPT samples.     

Characterization of cellulase under various intensities of static magnetic fields

The activity and secondary conformation of cellulase were investigated under static magnetic fields (0.15, 0.30, and 0.45 T). Compared to control group, activity and conformational change of cellulase were observed by means of UV spectrophotometer and far-UV circular dichroism detection after exposed in various static magnetic fields. The cellulase exhibited its maximal specific activity in the pH range of 4.0–4.6, and the optimal temperature was 60 °C. In addition, the circular dichroism spectra and kinetic parameters of cellulase have also been changed by magnetic fields.     

玉米芯糖化发酵生产燃料酒精的研究

利用正交试验对玉米芯发酵生产燃料酒精的条件进行了摇瓶试验。试验发现,采用管囊酵母SQY-001发酵生产酒精的最适条件为发酵温度36℃,发酵周期为72h,转速为100r/min,纤维素酶用量为40IU/(g·底物),并在此条件下得到酒精产率为0.152g/g。     

Neue Entwicklungen im Bereich Cellulase‐Engineering

Degradation of cellulose represents a key step for efficient generation of biofuels such as ethanol or butanol from non‐food crops. Several strategies aim to improve the performance of cellulases in order to make the overall process more cost‐efficient. In one strategy, novel arrangements of cellulases are developed. The resulting so‐called designer cellulosomes might allow equipping fermenting hosts with sufficient cellulase activity to grow on cellulose as sole carbon source and, thus, enable consolidated bioprocessing. Other strategies aim to engineer cellulases with higher thermostability and activity to make cellulose hydrolysis more efficient. Current developments in the field of cellulose engineering are summarized and achievements as well as limitations are highlighted.     

Effect of some thermal and chemical pretreatments on smoked Oyster mushroom quality

The effect of different thermal and chemical pretreatments on quality and enzyme activities of smoked mushroom was investigated. Mushrooms were blanched (water and steam) and dipped in different concentrations of sulphites (SO₂), hydrogen peroxide (H₂O₂), ethylene‐di‐amine tetra‐acetic acid (EDTA) and citric acid for 10 min before smoking. Enzyme activities, colour characteristics, microbiological and sensory examinations were carried out every 2 weeks up to 8 weeks of storage in refrigerator at 4 °C. Results could be concluded that smoked mushroom pretreated with SO₂, H₂O₂ and steam blanching had the best colour values, the better score for all sensory characteristics and lower non‐enzymatic browning compared with other pretreatments. The most effective pretreatment against total aerobic bacteria and yeast & moulds were citric acid, EDTA and steam, and then smoking of mushroom can be attributed to the reduction of microbial counts. The most effective pretreatments on quality and safety of smoked mushrooms were H₂O₂ and steam. It can be concluded that thermal and chemical treatments, rather than smoking of mushroom, reduce enzyme activities and are suitable to preserve mushrooms.     

New isolate of Trichoderma viride strain for enhanced cellulolytic enzyme complex production

A new Trichoderma viride stain was isolated from Singapore soil samples. Its mutants were developed by using ethyl methyl sulfonate (EMS) treatment and UV-irradiation followed by a semi-quantitative plate clearing assay on phosphoric-acid-swollen cellulose plates. Mutant EU2-77 proved to be the most promising extracellular cellulase producer among 20 mutants in a screening program performed in shake flask fermentation after plate screening. Soluble protein content, filter paper cellulase (FPase) activity, β-glucosidase activity and endoglucanase (CMCase) activity of the fermentation broths of the mutant strain were increased to 1.67, 2.49, 2.16, and 2.61 folds, respectively, compared with the wild strain. This enzyme complex produced by mutant EU2-77 contained FPase (2.19 IU/ml), CMCase (16.46 IU/ml), β-glucosidase (4.04 IU/ml), xylanase (42.37 IU/ml), and β-xylosidase (0.12 IU/ml). The soluble protein concentration in the enzyme complex was 1.69 mg/ml. The hydrolytic capacities of fermentation supernatants of T. reesei Rut-C30, the wild strain T. viride NP13a and mutant T. viride EU2-77 were compared with the commercial enzymes on the hydrolysis of waste newspaper. The crude enzymes prepared by T. viride EU2-77 showed much higher hydrolysis performance than that from the commercial strain Rut-C30 and demonstrated much comparable hydrolytic performances with the commercial enzyme mixtures. T. viride mutant EU2-77 produced high levels of extracellular cellulases as well as β-glucosidase, rendering the supplementation of β-glucosidase unnecessary in waste newspaper hydrolysis.     

酶法制取核桃多肽的工艺优化

运用Box-Behnken中心组合响应面分析法优化胰蛋白酶法提取核桃多肽的工艺条件,探讨了酶解过程中酶解pH值、温度和加酶量对核桃多肽提取的影响。优化工艺方案为:酶解pH7.0,温度45℃,加酶量5000U·g-1,其氨基氮的平均含量达到0.206%。     

Enzyme assisted extraction of luteolin and apigenin from pigeonpea [Cajanuscajan (L.) Millsp.] leaves

Luteolin and apigenin are naturally occurring flavones with a wide spectrum of pharmacological properties. In the present study, enzyme assisted extraction of luteolin and apigenin from pigeonpea leaves using commercial plant cell wall degrading enzyme preparations including cellulase, beta-glucosidase and pectinase were examined. We found that pectinase offered a better performance in enhancement of the extraction yields of luteolin and apigenin than cellulase and beta-glucosidase. The pectinase assisted extraction process was further optimized by varying different parameters such as pectinase concentration, time of incubation, pH of pectinase solution, and incubation temperature. The optimum parameters were obtained as follows: 0.4 mg/ml pectinase, incubation for 18 h at 30–35 °C, pH of pectinase solution 3.5–4. Under the optimum conditions, the extraction yields of luteolin and apigenin achieved 0.268 and 0.132 mg/g in pectinase treated sample, which increased 248% and 239%, respectively, compared with the untreated ones.