Journal of Biodiversity, Bioprospecting and Development

A process whereby a cell communicates and responses to external stimuli to alter plant growth, development, physiology and morphology is known as signal transduction. The integration of various signaling information and activities is important to generate a final response to the external stimuli. Protein kinases of protein phosphorylation are implicated in different signal transduction pathways in response to abiotic and biotic stress. Plants are always subjected to various ranges of abiotic and biotic stress. Protein phosphorylation is a post-translational modification process in which an amino acid residue of a protein is covalently modified by addition of a phosphate group involving an enzyme known as protein kinase. Protein kinases are among the most common cellular regulatory components of signal transduction in plants. Many studies demonstrate the prominent roles of protein kinases in the regulation of cell differentiation, growth and development of plant system. Plant growth is greatly affected by abiotic factors including low temperature, high salinity, osmotic stress, drought and biotic factors such as wounding as a result of invasion of various pathogens that eventually triggers the activation of plant defense system. Thus, this paper summarizes plant regulatory mechanisms of protein kinases via signal transduction process during abiotic and biotic stress. This paper also assesses the functional roles of protein kinases of phosphorylation in plant signaling pathways in response to abiotic and biotic stress. In a nutshell, in-depth knowledge about the roles of protein kinases is a prerequisite for the plant growth and development with their ability against various hostile environments.

Objective:Xylanase is a hydrolytic enzyme that breaks down backbone of xylan into xylose sugars. This extracellular enzyme possesses many applications in pulp and paper, food and beverage industries. Malaysia as an agricultural country contributes more than 5 million tons of agricultural wastes per year, thus, it is feasible to utilize agro-residual wastes to produce xylanase.

Methods:In the present study, Aspergillus brasiliensis ATCC 16404 was investigated for the production of xylanase in shake flask culture using different agro-residual wastes including wheat bran, sawdust, rice bran, sugarcane bagasse, barley husks, soybean hulls and palm kernel cake. A. brasiliensis was cultured at initial pH 6.5, agitation speed of 150 rpm at 30°C for 144 h. Thereafter, the optimised carbon sources obtained from earlier experiments were further elucidated in stirred tank bioreactor. This scaling up study was conducted using 1 L culture medium at initial pH 6.5, agitation speed of 200 rpm and aeration rate of 1 vvm.

Results: Based on our results, the highest xylanase activity of 11.2128 ± 1.7030 U/mL at 72 h was observed using pure substrate of xylan in shake flask culture. Agro-residual wastes of wheat bran and sawdust possessed appreciable xylanase activity of 1.1162 ± 0.0034 and 1.2343 ± 0.0809 U/mL in small scale of submerged fermentation [SmF], respectively. In order to replace the expensive xylan as the prime carbon source, wheat bran and sawdust were thus elucidated as the alternative carbon source in the scale up production of xylanase using stirred tank bioreactor system. Based on the result findings, A. brasiliensis yielded relatively higher and faster xylanase production of 3.1126 ± 0.2462 U/mL at 72 h using wheat bran compared to 1.1668 ± 0.0270 U/mL from sawdust at 96 h in bioreactor.

Conclusion:Hence, our study showed that wheat bran was the optimum cost effective substrate for the production of xylanase by A. brasiliensis in shorter fermentation period using large scale SmF in stirred tank bioreactor.

Bioprospecting activities tap vast sources of microbes from diverse and extreme habitats. Microbial hydrolases are important in the development of sustainable biomass energy or biofuels. To achieve full potential of this resource, there is a need to discover novel, unexploited microbes and their enzymes. So, a bioprospecting survey was conducted to identify fungal sources of biomass hydrolysing enzymes from different environments. Out of the total isolates, 39 were found to exhibit cellulolytic, hemicellulolytic and ligninolytic activities. Qualitative enzyme assays were performed using specific soluble substrates. Submerged fermentation of paddy straw/carrot grass (Parthenium hysterophorus) was then done to quantify the lignocellulolytic potential of all the isolates. The isolate CM20, identified to be Aspergillus terreus, was found to be a superior producer of cellulases and xylanases, while the isolate LG7, identified as Myrothecium roridum, was found to produce ligninolytic enzymes in high amounts. The study, therefore, resulted in the identification of cellulolytic and ligninolytic fungi which could be used in biorefineries for the development of greener energy.