ABSTRACT
Plant-associated microbes include taxonomically diverse communities of bacteria, archaebacteria, fungi, and viruses, which establish integral ecological relationships with the host plant and constitute the phyto-microbiome. The phyto-microbiome not only contributes in normal growth and development of plants but also plays a vital role in the maintenance of plant homeostasis during abiotic stress conditions. Owing to its immense metabolic potential, the phyto-microbiome provides the host plant with the capability to mitigate the abiotic stress through various mechanisms like production of antioxidants, plant growth hormones, bioactive compounds, detoxification of harmful chemicals and toxins, sequestration of reactive oxygen species and other free radicals. A deeper understanding of the structure and functions of the phyto-microbiome and the complex mechanisms of phyto-microbiome mediated abiotic stress mitigation would enable its utilization for abiotic stress alleviation of crop plants and development of stress-resistant crops. This review aims at exploring the potential of phyto-microbiome to alleviate drought, heat, salinity and heavy metal stress in crop plants and finding sustainable solutions to enhance the agricultural productivity. The mechanistic insights into the role of phytomicrobiome in imparting abiotic stress tolerance to plants have been summarized, that would be helpful in the development of novel bioinoculants. The high-throughput modern approaches involving candidate gene identification and target gene modification such as genomics, metagenomics, transcriptomics, metabolomics, and phyto-microbiome based genetic engineering have been discussed in wake of the ever-increasing demand of climate resilient crop plants.
ABSTRACT
CONTEXT: Xylanase constitutes 20% of world enzyme market. Significantly, they are used in poultry feed, paper pulp, bakery, and textile industries. In view of the increasing demand of the enzyme, it is vital to develop indigenous strains and scalable technologies for the production of industrial enzymes. AIMS: The objective of the present paper was to isolate a high-yielding strain of thermo-alkali-stable xylanase-producing bacteria for potential application in paper and pulp and biofuel industry. METHODS: Sampling for prospecting of suitable organism was carried out from the places with dead and decaying lignocellulosic waste, and then Congo red screening was employed for the primary isolation of xylanase producers. RESULTS: We report the isolation of 18 different strains of xylanase producer bacteria from natural hot water geyser of Sohna, Haryana, India. Subsequently, two of these isolates were chosen for further studies based on xylanase yield and desirable properties such as thermostability and alkali stability of xylanase produced. CONCLUSION: Isolate B2 was later identified as Bacillus licheniformis, whereas isolate Y3 was identified as Brevibacillus borstelensis. This strain when cultured at 35°C for 72 h showed xylanase production at 128 U/ml. The molecular weight of xylanase was determined to be 25 kDa. The production was scaled up in a 5-L stirred-tank bioreactor which led to high xylanase concentration of 380 U/ml in the first 48 h of culture.
