Current Biotechnology - Volume 7, Issue 3, 2018

Background: Despite considerable studies on the usage of enzymes for the recycling of different types of waste papers containing various ink compositions, there is no systematic review outlining the role of fungal enzymes. This review article emphasizes on the different mechanisms of fungal enzyme (cellulase, xylanase, amylase, lipase, etc.) action on the fibre surface to remove ink particles. Therefore, the present review will cover the prospects and development of different fungal enzymes applied in recycling of waste papers including current research on laboratory, pilot and mill scales. Methods: We undertook a year-wise search of peer-reviewed research literature mainly focused on cellulase, hemicellulase, lipase, amylase enzymes used for the waste papers recycling. These research articles were screened for the enzymes of fungal origin. Further, the search was extended to gather data from the mill scale trials of fungal enzymes. The characteristics of screened papers were described. The evaluation of the fungal enzymes was done on the basis of effective residual ink concentration, brightness, strength properties, pulp freeness and effluent load. Results: One hundred one peer reviewed research papers were included in the present review. Enzymatic deinked pulps showed improved deinking efficiency, drainage, strength properties, pulp brightness along with lower residual ink, chemical usage and environmental load than the conventional chemically deinked pulps. Higher enzyme dose and longer reaction time may be detrimental for the fibre, which result in reduced strength properties of paper. Sometimes high BOD may also be observed due to the use of cellulases and hemicellulases. Conclusion: This review article confirms the importance of fungal enzymes for the recycling of different types of waste papers, which have been proven as green technology with improved performance. The literature we have reviewed showed that there is the utmost need to further improve the performance of enzymes towards the deinking through genetic engineering.

Background: The search for natural bioactive metabolites having potential anticancer property dates back to the Ebers papyrus written in 1550 BC. Natural products from medicinal plants and microorganisms are the most consistent and productive source for the “first-in-class” drugs. After two decades of research, a great deal of interest has been generated by discovery of remarkable pharmacological agents from endophytic fungi residing asymptomatically within plant tissues. Objective: This review substantially covers the novel cytotoxic compounds isolated from endophytic fungi associated with terrestrial and mangrove plants as well as other microorganisms such as lichens, during 2011- 2015. These natural compounds are described based on their cytotoxic activity profiles, chemical nature and potential structure–activity relationship deduced from the biochemical and cytotoxic studies. The anti-cancerous activities of the compounds discussed in this review are taken from the published reports exhibiting activity against specific cancer cell lines along with the mechanism of action. These compounds are exclusively isolated from endophytic fungi. Conclusion: Endophytic fungi can be exploited for isolation of new reliable, economical and environmentally safe natural bioactive molecules having wide range of applications in agriculture, medicine and food industry. Over the past few decades much progress has been achieved though, still many issues such as optimizing the fermentation culture conditions for increasing the compound yield, elucidating biosynthetic pathway of the compounds in the endophytic fungi needs to be further clarified and resolved.

Background: The asymptomatic fungal endosymbionts of plants called the endophytes are universal in their occurrence. The occurrence of some entomopathogenic fungi which infect and kill insect pests of crops as endophytes provides an excellent opportunity for using these fungi in biocontrol. A few studies substantiate this novel approach of pest management; however, since this facet of endophyte research is nascent, enquiries answering basic questions on various aspects of endophyte biology are essential to successfully implement endophyte-mediated biocontrol. In a collaborative research, we addressed a few of these questions including (i) to what extent do fungal genera reported to have entomopathogenic species colonize non-crops as endophytes? (ii) can an endophyte from a non-crop source and vested with anti-insect property survive as an endophyte when introduced into a crop? (iii) how does an anti-insect endophyte in a crop affect an insect pest? and (iv) can endophytes be used for controlling weeds? The results of this study show that endophytes have enormous potential as biocontrol agents and reiterate the need for concerted efforts to obtain more basic information about endophyte biology before they can be used effectively for biocontrol. Methods: Non-entomopathogenic but anti-insect metabolites producing endophytes from plant and nonplant sources are shown to have potential biocontrol properties. Survival of an effective fungus from an alien source in a crop plant as an endophyte has been shown to be only for a limited period. Endophytes are shown to possess weedicidal activity. Results: Entomopathogenic fungal genera rarely colonize leaves of forest trees as foliar endophytes. Non-entomogenous endophytes produce anti-insect compounds affecting pests of crops thus having the potential as biocontrol agents. Such fungi isolated from non-plant sources can be inoculated into crops to function as endophytes, for brief periods. Insect pests avoid crops with anti-insect endophytes for oviposition and feeding. Some endophytes elaborate weedicidal compounds. Conclusion: Our basic study underscores the need to screen plants and non-plants of different habitats for entomopathogenic and anti-insect endosymbiotic fungi. Futhermore, it highlights the importance of screening endophytes for weedicidal compounds. We emphasise the need for focused studies for better understanding of the interaction between endophytes and their plant hosts and the biotic stressors of the host plants to enhance the success of using endophytes for biological control.

Background: Fermentation technology is hailed as an important tool for large scale production of food flavours. Among the microbial sources, importance of yeasts for production of flavour and fragrance molecules is on the rise due to their nonhazardous, diverse metabolic nature as well as amenability to strain modifications and process optimization. It is therefore, highly appropriate to comprehesively cover various aspects of food flavour production by yeasts and present up-to-date information on aroma compounds from yeasts in a single manuscript. Objective: This review article has been prepared with the major objective to systematically and meaningfully compile the scientific developments on the use of yeasts as a source of food flavours and present a direction for future line of work. Main Findings of the Study: Published literature shows production of a variety of food flavour molecules, viz., fusel alcohols, esters, lactones, aldehydes, ketones, pyrazines and terpenoids by yeasts belonging to different genera, such as Saccharomyces, Kluyveromyces, Pichia, Hanseniospora, Yarrowia, Candida etc. The major impediment in large scale production of flavour molecules by yeasts has been low production and productivity in their conventional growth media. Therefore, it becomes important and pertinent to optimize processes involving important fermentation parameters, such as carbon and nitrogen sources, oxygen transfer rate, aeration levels etc, in improving the production of flavour compounds by yeasts. Strain improvement of the known flavour producing yeasts using advanced biotechnological tools is the need of an hour for improving the production capability of such yeasts. Therefore, combining process optimization approaches and strain improvement is likely to result in higher productivity of food flavours by different yeasts. Conclusion and Potential Application: This paper presents a comprehensive review on yeast sources, strain improvement and process optimization research for food flavour production by yeasts. Future research should be directed towards combining the strain improvement approaches with new process optimization methods to improve the flavour production by yeasts. Thus, it can be used as a ready reckoner by the researchers to get an overview of the research developments in yeast derived flavours for their future research work.

Background: Fungal chitin and chitosan have emerged as the most versatile and promising functional biopolymers with technologically potent biotechnological applications. They have a wide array of applications due to their outstanding features such as non toxicity, biodegradability, biocompatibility and eco-friendly. The biotechnological production of chitin and chitosan from fungal sources has gained extensive worldwide attention in the recent years due to their potential and technological advantages over conventional production of chitin and chitosan from the shell wastes of Crustacea, such as shrimp, crab, prawn and crayfish. Methods: We review technical papers, reviews and other articles related to fungal chitin and chitosan, which have emerged as the most versatile and promising functional biopolymers with technologically potent biotechnological applications. Results: This review recapitulates the recent advances in the biotechnological production of fungal chitin, chitosan and their derivatives, and with focus on their application in pharmaceuticals, food industries, agricultural and environmental sectors and in the treatment of industrial effluents. Conclusion: Fungal biotechnology offers advantages in the production of fungal chitin and chitosan over classical processing procedures because these materials can be produced in a controlled environment throughout the year and the extraction process is simple, economically attractive and requires less harsh solvents resulting in reductions in the time and cost of production.

Background: Heavy metals are continuously being mobilized into the biosphere either through natural mechanisms or through anthropogenic activities. Ectomycorrhizal fungi forms a symbiotic association with the plant roots and helps them in enhancing growth and protects the plant from various biotic as well as abiotic stresses. Objective: The focus of this review is to comprehend the role of metallothioneins and glutathione metabolism in heavy metal detoxification in ectomycorrhizal fungi. Method: Numerous research papers, articles and chapters have been reviewed to study the mechanisms involved in heavy metal chelation in different organisms. Ectomycorrhizal fungi chelate the metals intracellularly by producing metallothioneins and glutathione. The chelation mechanism has been broadly studied. Results: Ectomycorrhizal fungi play an important role in metal homeostasis by producing intracellular chelators like metallothioneins and glutathione. These chelators are rich in cysteine, having high affinity for binding heavy metals and detoxify them. Conclusion: Since ectomycorrhizal fungi thrive on the metal polluted soil, they become the most potent candidates for bioremediation of the metal polluted soil. Therefore it is necessary to understand the key mechanisms involved in this detoxification process.

Background: Considerable evidences shows that inulinases are important industrial enzymes; however, the information on microbial sources, characteristics, and applications of inulinases is scattered in the available literature. Therefore, this study aimed to collate all information, particularly on fungal sources, characteristics, and applications of inulinases. Methods: Peer-reviewed research articles were searched in bibliographic databases in a conceptual mode using inclusion of new findings/exclusion of repeated methodology. In this substantial review, each screened paper is described and its findings are proposed as viewpoints. Results: In the present review, various properties of inulin as a potent substrate for inulinase production are summarized. Many inulin-containing plants and the applications of inulin in the food industry have been reported. In addition, extended data on inulinase producing fungal strains have also been reviewed. The progress in inulinase production under submerged and solid-state fermentation is presented along with the description of innovations used in the production of recombinant inulinases. Furthermore, this review highlights the various physico-chemical characteristics of fungal inulinases to determine their suitability for industrial use. Besides, various promising applications and aspects of enzymatic hydrolysis for producing important industrial products also have been discussed. Conclusions: Inulinases are important industrial hydrolysing enzymes which are generally used for the production of high fructose syrup and fructooligosaccharides. Biochemical, biophysical properties and structure-function analysis elucidates the substrate specificity of enzyme as well as its phylogenetic evolution and relationship. However, to expand the utility of inulinases in various industries, an extensive investigation for novel microbial sources should be conducted and low cost substrates, and improved bioprocessing technology should be used.