Adeline Su Yien Ting

Alginate-immobilized bentonite clay: Adsorption efficacy and reusability for Cu(II) removal from aqueous solution

This study evaluated the use of alginate-immobilized bentonite to remove Cu(II) as an alternative to mitigate clogging problems. The adsorption efficacy (under the influence of time, pH and initial Cu(II) concentration) and reusability of immobilized-bentonite (1% w/v bentonite) was tested against plain alginate beads. Results revealed that immobilized bentonite demonstrated significantly higher sorption efficacy compared to plain alginate beads with 114.70 and 94.04 mg Cu(II) adsorbed g(-1) adsorbent, respectively. Both sorbents were comparable in other aspects where sorption equilibrium was achieved within 6 h, with optimum pH between pH 4 and 5 for adsorption, displayed maximum adsorption capacity at initial Cu(II) concentrations of 400 mg l(-1), and demonstrated excellent reusability potential with desorption greater than 90% throughout three consecutive adsorption-desorption cycles. Both sorbents also conformed to Langmuir isotherm and pseudo-second order kinetic model. Immobilized bentonite is therefore recommended for use in water treatments to remove Cu(II) without clogging the system.

Efficacy and reusability of alginate-immobilized live and heat-inactivated Trichoderma asperellum cells for Cu (II) removal from aqueous solution

Cu(II) removal efficacies of alginate-immobilized Trichoderma asperellum using viable and non-viable forms were investigated with respect to time, pH, and initial Cu(II) concentrations. The reusability potential of the biomass was determined based on sorption/desorption tests. Cu(II) biosorption by immobilized heat-inactivated T. asperellum cells was the most efficient, with 134.22mg Cu(II) removed g(-1) adsorbent, compared to immobilized viable cells and plain alginate beads (control) with 105.96 and 94.04mg Cu(II) adsorbed g(-1) adsorbent, respectively. Immobilized non-viable cells achieved equilibrium more rapidly within 4h. For all biosorbents, optimum pH for Cu(II) removal was between pH 4 and 5. Reusability of all biosorbents were similar, with more than 90% Cu(II) desorbed with HCl. These alginate-immobilized cells can be applied to reduce clogging and post-separation process incurred from use of suspended biomass.

Endophytic l-asparaginase-producing fungi from plants associated with anticancer properties

Endophytes are novel sources of natural bioactive compounds. This study seeks endophytes that produce the anticancer enzyme l-asparaginase, to harness their potential for mass production. Four plants with anticancer properties; Cymbopogon citratus, Murraya koenigii, Oldenlandia diffusa and Pereskia bleo, were selected as host plants. l-Asparaginase-producing endophytes were detected by the formation of pink zones on agar, a result of hydrolyzes of asparagine into aspartic acid and ammonia that converts the phenol red dye indicator from yellow (acidic condition) to pink (alkaline condition). The anticancer enzyme asparaginase was further quantified via Nesslerization. Results revealed that a total of 89 morphotypes were isolated; mostly from P. bleo (40), followed by O. diffusa (25), C. citratus (14) and M. koenigii (10). Only 25 of these morphotypes produced l-asparaginase, mostly from P. bleo and their asparaginase activities were between 0.0069 and 0.025 μM mL−1 min−1. l-Asparaginase producing isolates were identified as probable species of the genus Colletotrichum, Fusarium, Phoma and Penicillium. Studies here revealed that endophytes are good alternative sources for l-asparaginase production and they can be sourced from anticancer plants, particularly P. bleo.

Investigating metal removal potential by Effective Microorganisms (EM) in alginate-immobilized and free-cell forms

Metal removal potential of both alginate-immobilized and free-cells of Effective Microorganisms (EM-1™ Inoculant) was investigated in this study. Results revealed that removal of Cr(III), Cu(II) and Pb(II) followed a similar trend where alginate-immobilized EM were more efficient compared to free-cells of EM. For these metals, 0.940, 2.695 and 4.011 mg g(-1) of Cr(III), Cu(II) and Pb(II) were removed compared to only 0.160, 0.859 and 0.755 mg ml(-1) removed by free-cells, respectively. The higher efficiency of alginate-immobilized EM was primarily attributed to the alginate matrix. This was evident when both alginate-immobilized EM and plain alginate beads (without EM), were not significantly different in their removal efficacies. Presence of alginate also enhanced the use of the biosorbents as maximum metal sorption was achieved after 120 min as opposed to only 60 min for free-cells. EM per se in immobilized or free-cell forms did not enhance metal removal efficacy.

Induction of host defence enzymes by the endophytic bacterium Serratia marcescens, in banana plantlets.

Pre-inoculation with the endobacterium Serratia marcescens (strain UPM39B3) induced the production of host defence enzymes such as peroxidase, polyphenoloxidase, phenylalanine ammonia lyase, total soluble phenols and lignothioglycolic acid in banana plantlets. The levels of these enzymes were evidently higher in plantlets pre-treated with the endobacterium compared to the control. The production of host-induced enzymes benefitted the crop plants as they may have a role in suppressing Fusarium wilt incidence in the plantlets. This was evident when plantlets pre-treated with the endobacterium showed a lower disease severity (50%) compared to diseased plantlets lacking the endobacterium (74%). The results of this study thus highlight the potential of the isolate Serratia marcescens (strain UPM 39B3) as a biological control agent for Fusarium wilt management in bananas, reducing disease severity via stimulation of host defences.

Biocontrol of Fusarium oxysporum f.sp. cubense tropical race 4 by formulated cells and cell-free extracts of Streptomyces griseus in sterile soil environment

The biocontrol activities of cells and cell-free extracts of Streptomyces griseus was tested against Fusarium oxysporum f.sp. cubense tropical race 4 (FOC race 4) in a sterile soil environment. They were first formulated in sodium alginate, kaolin clay and in alginate–kaolin combination, prior to introducing into sterile soil inoculated with 6 log10 cfu FOC race 4 g−1 soil. Results revealed that bioformulated cells of S. griseus, irrespective of the materials used, were generally more effective in inhibiting growth of FOC race 4 when compared to non-formulated cells of S. griseus. Kaolin was the most suitable inert material as formulation of S. griseus with kaolin effectively suppressed FOC race 4, with only 5.40 log10 cfu g−1 of FOC race 4 recovered after 20 days. Kaolin formulations also allowed good cell recovery post-formulation. Alginate was less desirable as poorer control was demonstrated, with 6.12 and 6.16 log10 cfu g−1 of FOC race 4 recovered from soils treated with alginate only and alginate–kaolin formulated S. griseus, respectively. Bioformulations did not benefit cell-free extracts at all. Our study suggests formulation of cells of S. griseus is more beneficial than cell-free extracts and kaolin is the preferred material for formulation.

Biosourcing Endophytes as Biocontrol Agents of Wilt Diseases

Endophytes are the centre of many investigations in the recent years, mainly for their role as biological control agents towards various pathogens. Of the many types of phytopathogens, wilt pathogens are thought to benefit the most from application of endophytes. Wilt pathogens colonize internal plant tissues, especially the vascular tissues, which are also a common colonization niche for endophytes. The pre-colonization of biocontrol endophytes has been shown to render some form of protection to the host plant, resulting in disease suppression when challenged with the pathogen. Investigations to identify potential biocontrol agents are commonly initiated by performing extensive isolation and screening of endophytes from various asymptomatic host plants. This is followed by in vitro assays with selected pathogens, with various mechanisms of their antagonistic interaction established. Isolates with strong biocontrol activities are subsequently tested at the glasshouse and field stage to determine biocontrol efficacy. To date, tremendous progress has been made in understanding the diversity and mechanisms of control of endophytes against wilt pathogens. Their biocontrol efficacies are evident in laboratory screenings and glasshouse trials. In field trials however, poor control efficacy is often observed, attributed to the influence of indigenous microflora in the soil and environmental conditions. To address these limitations, bioformulation of endophytes is explored. This article will discuss the endophytes identified as biocontrol agents against wilt pathogens, the typical methods for biosourcing of these biocontrol endophytes, the challenges in implementing endophytes for wilt control and strategies to address these limitations.

Understanding colonization and proliferation potential of endophytes and pathogen in planta via plating, polymerase chain reaction and ergosterol assay.

Graphical abstract Colonization and proliferation potential of endophytes and pathogen in planta via ergosterol assay and compared to conventional plating and PCR methods.

Microfungi for the Removal of Toxic Triphenylmethane Dyes

Triphenylmethane (TPM) dyes are a group of aromatic, synthetic dyes used widely in industrial processes. The discharge of these dyes into the environment demands strict monitoring and treatment due to their toxicity and cancer-inducing possibilities. The inexpensive, environmental-friendly biological treatment of TPM dyes using microfungi is an attractive remediation approach compared to the conventional physico-chemical methods. A diverse population of microfungi (comprising of members with microscopic fruiting bodies), such as white-rot and non-white-rot fungi, have demonstrated potential in removing TPM dyes via biosorption and biodegradation. Enzymes involved in dye decolourization include laccase, lignin peroxidase, manganese peroxidase and reductases. The biosorption and biodegradation activities of microfungi are influenced by nutrients, pH, temperature, initial dye concentration and biomass concentration. This chapter discusses the various strains of microfungi with TPM dye-decolourizing potential, as well as their mechanisms, optimum conditions and some current technological applications for these useful microfungi to remove TPM dyes.

Trichoderma asperellum cultured in reduced concentrations of synthetic medium retained dye decolourization efficacy

Trichoderma asperellum (Ta) was first cultured in synthetic medium (Potato Dextrose Broth, PDB) of various concentrations (100, 75, 50, 25%). The biomass was harvested and inoculated into dye solutions (crystal violet, CV; methyl violet, MV; malachite green, MG; and cotton blue, CB). Reduced concentrations (20, 50, 75%) affected growth rate but their decolourization efficacies remained unaffected. This was attributed to similar numbers and types of functional groups (hydroxyl, amine, ester-lipid, alkane groups) found on the surface of fungal biomass, as revealed by the Fourier transformed infrared spectroscopy (FTIR) analysis. Their production of NADH-reductase for degradation, and their biosorption activities were also unaffected. In general, Ta cultured in reduced concentrations (20, 50, 75%) retained the ability to perform biosorption and biodegradation, similar to cultures from control (100% PDB). This suggested that reduced nutrient levels (as a cost-feasible strategy) could be used to cultivate biomass of Ta for dye removal activities.