Paul Manish, Nayak Dipti Pravamayee, Thatoi Hrudayanath
Department of Biotechnology, North Orissa University, Takatpur, Baripada, Odisha, 757003, India.
J Genet Eng Biotechnol. 2020 Dec 11;18(1):81. doi: 10.1186/s43141-020-00099-7.
Xylanase has long been recognized as a widely used industrially important enzyme. There are some bacterial species already reported to produce xylanase which have potent xylanolytic activity towards the use of this enzyme in the production of bioethanol from lignocellulosic biomass. In this view, an efficient xylanolytic bacterial strain was isolated and screened from the soil sample of Simlipal Biosphere Reserve. Enzymatic assay for the xylanase activity was evidenced from the most potent bacterial strain, and the culture condition was optimized for obtaining the maximum enzyme activity. The most potent xylanolytic strain was also identified using biochemical and molecular methods.
Nineteen xylanolytic bacteria (SXB1-SXB19) were isolated from Simlipal forest soil samples following dilution plate technique using corn cob xylan-enriched nutrient agar medium and screened for their xylanase-producing ability. Among these isolates, SXB19 showed maximum xylanolytic potential with a halozone size of 2.5 cm as evident in the formation of prominent yellow patches surrounding its growth in xylan-enriched nutrient agar plate. In unoptimized condition, SXB19 showed the highest enzymatic activity of 22.5 IU/ml among the 19 bacterial strains. In order to optimize the culture conditions for maximizing the xylanase production, Box-Behnken design of response surface methodology (RSM) was used. Four variables such as incubation time, pH, substrate (corn cob xylan) concentration, and temperature were considered for the RSM optimization study. From the results, it is evident that in an optimized condition of incubation time 36 h, pH 6.0, xylan concentration 0.5%, and temperature 42.5 °C, the enzyme activity reached a maximum of 152 IU/ml with nearly 6.75 times increase from the unoptimised condition. Besides, xylanase production from SXB19 was considerable in the presence of xylan followed by starch, nitrogen source such as urea followed by yeast extract, and mineral ion sources such as KCl followed by MgSO and ZnSO. From different biochemical tests, 16S rRNA gene sequencing, and phylogenetic analysis, the bacterial strain SXB19 was identified as Pseudomonas mohnii.
The isolation of Pseudomonas mohnii, a potent xylanolytic bacterium from Simlipal, is a new report which opens up an opportunity for industrial production of xylanase for bioethanol production and other applications.
木聚糖酶长期以来一直被认为是一种广泛应用的重要工业酶。已有一些细菌物种被报道能产生木聚糖酶，这些酶对利用木质纤维素生物质生产生物乙醇具有强大的木聚糖分解活性。基于此，从西姆利帕尔生物圈保护区的土壤样本中分离并筛选出了一株高效的木聚糖分解细菌菌株。对最具潜力的细菌菌株进行了木聚糖酶活性的酶学测定，并对培养条件进行了优化以获得最大酶活性。还使用生化和分子方法对最具潜力的木聚糖分解菌株进行了鉴定。
采用稀释平板技术，使用富含玉米芯木聚糖的营养琼脂培养基从西姆利帕尔森林土壤样本中分离出19株木聚糖分解细菌（SXB1 - SXB19），并筛选了它们产生木聚糖酶的能力。在这些分离株中，SXB19表现出最大的木聚糖分解潜力，在富含木聚糖的营养琼脂平板上其生长周围形成明显的黄色斑块，晕圈大小为2.5厘米。在未优化的条件下，SXB19在19株细菌菌株中表现出最高的酶活性，为22.5 IU/ml。为了优化培养条件以最大化木聚糖酶的产量，采用了响应面法（RSM）的Box - Behnken设计。在RSM优化研究中考虑了四个变量，即培养时间、pH、底物（玉米芯木聚糖）浓度和温度。结果表明，在培养时间36小时、pH 6.0、木聚糖浓度0.5%和温度42.5℃的优化条件下，酶活性达到最大值152 IU/ml，比未优化条件下增加了近6.75倍。此外，在有木聚糖存在的情况下，SXB19产生的木聚糖酶量可观，其次是淀粉；氮源方面，尿素其次是酵母提取物；矿物离子源方面，KCl其次是MgSO和ZnSO。通过不同的生化试验、16S rRNA基因测序和系统发育分析，细菌菌株SXB19被鉴定为莫氏假单胞菌。
从西姆利帕尔分离出的高效木聚糖分解细菌莫氏假单胞菌是一项新的报道，为工业生产用于生物乙醇生产及其他应用的木聚糖酶开辟了机会。
