Identification and Characterisation of Seed-Borne Fungal Pathogens Associated with Maize (Zea mays L.)

A research study was conducted to identify and characterise seed-borne fungal pathogens associated with maize (Zea mays L.) in storage. Seed-borne fungal pathogenic infections of maize were studied using seed samples collected from Gokwe South District in Zimbabwe. The agar plating method using PDA medium was used to detect fungal pathogens on the maize seeds. A total of 150 treatments were used for this experiment, which were replicated three times in a randomised complete block design (RCBD). Analysis of the grain showed the presence of Fusarium moniliforme, Rhizopus stolonifer, Penicillium citrinum, and mostly Aspergillus species, namely, Aspergillus flavus, Aspergillus parasiticus, Aspergillus niger, and Aspergillus tamarii. Significant differences ( p < 0.05) between treatments were detected for the pathogens. A total of ten samples were used for mycotoxin determination, and all of them were 100% positive with aflatoxin total, zearalenone, fumonisin, and deoxynivalenol (DON) having an average of 0.255 ppb, 2.425 ppb, 2.65 ppb, and 0.07 ppb, respectively. The present study showed that most grain samples are contaminated with different species of fungi with mycotoxigenic potential. The data on the diversity and magnitude of pathogen infection by fungal species will have a significant effect even at the regional level for predicting the extent of pre- and postinfections. Measures to reduce mycotoxin contamination are needed for maize grains.

Characterisation and Pathogenicity of Aspergillus tamarii Causing Banana Fruit Rot

Banana fruit rot is a common postharvest disease of the banana fruit. The appearance of rot symptoms on the surface of the fruits reduces the quality and marketability of banana. From rot lesions on banana fruits, three Aspergillus isolates were isolated. Based on morphological characteristics and sequences of Internal Transcribed Spacer, β-tubulin and calmodulin, the isolates were identified as A. tamarii. Pathogenicity tests of the isolates, conducted using mycelial plugs with wounded and unwounded treatments, showed A. tamarii as the pathogen of banana fruit rot. Rot symptoms were highly severe on wounded banana fruits compared to unwounded fruits, and therefore, wounded banana fruits are more susceptible to A. tamarii infection. To the best of our knowledge, this is the first report of A. tamarii as a causal pathogen of banana fruit rot. This study indicated A. tamarii is one of postharvest rot pathogens of banana.

Utilizing a novel fungal enzymatic cocktail as an eco-friendly alternative for cellulose pulp biobleaching

Enzyme cocktails can alter the lignin and hemicellulose content in wood cell walls, improving the bleaching process during pulp production and offsetting the need for toxic chemicals. In this study, brown pulp was biobleached with a mixture of crude fungal extracts rich in xylanase and laccase, respectively produced from Aspergillus tamarii Kita and Trametes versicolor on waste materials. The optimal conditions for biobleaching were a mixture of xylanase and laccase crude extracts (1 to 2 v/v), at a temperature of 36 °C and a pH of 5.5. The treated brown cellulose pulp showed a reduction in the Kappa number by 1.83 points, representing an efficiency of 20.3%. In addition, the brightness increased by 4.65 points in comparison to the control. Hence, studies involving the application of the standardized cocktail during the hydrolysis of lignocellulosic residues, e.g., barley residue and sugarcane bagasse, led to the formation of 85 g/L and 25 g/L of reducing sugars, respectively. Moreover, the standardized cocktail caused greater deinking of the recycled paper pulp.

Use of a Sequential Fermentation Method for the Production of Aspergillus tamarii URM4634 Protease and a Kinetic/Thermodynamic Study of the Enzyme

Microbial proteases are commonly produced by submerged (SmF) or solid-state fermentation (SSF), whose combination results in an unconventional method, called sequential fermentation (SF), which has already been used only to produce cellulolytic enzymes. In this context, the aim of the present study was the development of a novel SF method for protease production using wheat bran as a substrate. Moreover, the kinetic and thermodynamic parameters of azocasein hydrolysis were estimated, thus providing a greater understanding of the catalytic reaction. In SF, an approximately 9-fold increase in protease activity was observed compared to the conventional SmF method. Optimization of glucose concentration and medium volume by statistical means allowed us to achieve a maximum protease activity of 180.17 U mL−1. The obtained enzyme had an optimum pH and temperature of 7.0 and 50 °C, respectively. Kinetic and thermodynamic parameters highlighted that such a neutral protease is satisfactorily thermostable at 50 °C, a temperature commonly used in many applications in the food industry. The results obtained suggested not only that SF could be a promising alternative to produce proteases, but also that it could be adapted to produce several other enzymes.

Myco-Fabricated Gold Nanoparticles from Aspergillus Tamarii MTCC5152, its Characterization and Dye Biodegradation

This work was initiated to investigate the myco-fabrication of gold nanoparticles (AuNPs) using a fungal strain, Aspergillus tamarii 5152 (A. tamarii MTCC 5152). The biosynthesized gold nanoparticles were characterized by visual observation, and using UV-Vis and FTIR spectroscopy, DSC, TGA, Zeta-potential, DLS and SEM analyses. NADH-dependent cofactor analysis and photocatalysis assays were carried out for NADH-dependent AuNPs biosynthesis and dye degradation ability. A maximum surface plasmon resonance peak for the AuNPs was recorded at 535 nm, followed by the identification of protein capping effect of the extract by FTIR spectroscopy. The average size (Z) of the nanoparticles observed was 39.15 nm, while SEM images showed crystallized rod-shaped structures ranging from 55-91 nm. A negative zeta potential of 10.5 mV showed repulsion between the nanoparticles, which indicates the stabilizing power of the fungal extract. Further, it was observed that NADH acts as a cofactor for the nanoparticle biosynthesis. The AuNPs were found to degrade crystal violet dye by 63%. From this study, it can be understood that the process of fungal mediated biosynthesis of AuNPs by A. tamarii MTCC 5152 is simple, less expensive, and could be utilized for bioremediation of toxic dye accumulation.

Isolation and Molecular Identification of some Fungi Associated with Jatropha curcas (L.)

Jatropha curcas is a plant of great economic importance that experiences high incidence of fungal attack. Misidentification of the fungal species is bound to occur with the use of traditional cultural methods where organisms are identified morphologically and/or microscopically. This study was carried out to isolate and identify the fungi associated with Jatropha curcas (L.) using both traditional/ cultural techniques and molecular methods. The fungi were isolated from diseased leaves and stems of J. curcas using both Standard Blotter and Potato Dextrose Agar (PDA) methods. DNA was extracted from the fungal isolates using Zymo Fungal/Bacteria DNA MiniPrep Kit. Amplification of the Internal Transcribed Spacer (ITS) regions of the fungal isolates was carried out using fungi universal primer pairs for ITS4 and ITS5. The amplicons were sequenced and the isolates were identified as Penicillium brevicompactum, Aspergillus sp., Botryosphaeria rhodina, Aspergillus nomius, Aspergillus tamarii, Rhizopus oryzae, Penicillium citrinum and Fusarium solani. Phylogenetic analysis was carried out to know the relationship between the isolates and other closely-related species in GenBank. Jatropha curcas is colonized by many fungal species some of which may be pathogenic to the plant, and molecular techniques pose the best alternative for accurate identification of these organisms. Keywords: Jatropha curcas, fungi, polymerase chain reaction, phylogeny, sequencing