Entomopathogenic fungi in population of Zonocerus variegatus (l) in Ibadan, south west, Nigeria

Field survey of population of Zonocerus variegatus revealed a high fungal incidence of 76% when Sporulation tests were carried out on grasshoppers cadaver. Eight fungi with differing incidence rates were isolated. These are Fusarium sp. (8%); Beauveria bassiana (18%); Metarhizium sp. (20%); Aspergillus flavus (10%); Penicillium sp. (13%) Aspergillus niger (14%); Mucor sp. (13%) and unidentified fungus (4%). Fungal isolates virulence bioassay response showed that B. bassiana had the highest lethal time (LT50) of 2 days. Metarhizium sp with LT50 of 5 days was selected in lieu of A. niger which does not prove to be pathogenic to grasshoppers. The results were discussed in relation to the ecology of fungal pathogens of the variegated grasshopper and their possible role in control of Z. variegatus in the agroecosystem of south west, Nigeria. Key words: Fungal ecology, entomopathogenic fungi, Zonocerus variegatus infection incidence. African Journal of Biotechnology Vol.3(8) 2004: 382-38

Growth pattern and structural nature of amylases produced by some Bacillus species in starchy substrates

The growth pattern and microbial biomass formed during metabolic activities of the Bacillus species on starchy substrates was determined. The result showed that the strains B. subtilis (WBS), B. licheniformis (WBL) and B. coagulans (MBC) generally had high growth rate. B. circulans (SBC) and B. coagulans (WBC) has specific affinity for growth and some enzymatic activity on corn starch medium compared with other lower growth observed in B. polymyxa (WBP) but higher enzyme production. The amylolytic Bacillus species obtained utilized white corn starch substrate as a sole carbon source as well as soluble starch. The amylase production values range from 0.022 x 102 unit/cfu in B. circulans (WBC) to 0.912 x 102 unit/cfu in B. licheniformis (WBL) for corn starch, and 0.01 x 102 unit/cfu in both B. megaterium (SBG) and B. licheniformis (SBL) to 0.693 x 102 unit/cfu in B. subtilis (WBS) for soluble starch.Keywords: Activity, Bacillus, enzymatic, metabolic, starchy, substrat

Heat activation and stability of amylases from Bacillus species

Leitch and Collier sporulating Bacillus medium was used to isolate some strains of Bacillus species from soil, wastewater and food sources in Ibadan, Oyo State, Nigeria, by heat activation method. Heat treatment at 80oC allowed the growth of sporulating Bacillus species, in the culture sample source without other bacteria forms. The amylolytic Bacillus species isolated during the study were identified as Bacillus macerans, Bacillus coagulans Bacillus licheniformis, Bacillus circulans, Bacillus megaterium, Bacillus polymyxa and Bacillus subtilis. Heat treatment at 70oC denatured the -amylase component of the amylase source while -amylase retained its potency at this temperature. Calcium cations (Ca2+) enhance the enzyme production than Na+ which was less effective. Physiological studies show that an optimum temperature of 40oC was suitable for the enzyme activity while temperature above 60oC reduced its activity unless positive measures are taken to stabilize it with relevant cations like Ca2+

Microbial control of caged population of Zonocerus variegatus using Beauveria bassiana and Metarhizium sp.

Microbial control of caged populations of Zonocerus variegatus was carried out using indigenous fungal entomopathogens isolated from the grasshopper's cadaver. Bioassay response indicated a dose-dependent mortality coupled with drastic reduction in food consumption among spores infected grasshoppers. Lethal time (LT50) of 4.6 days for 103 spores/ml and 3.8 days for 107 spores/ml of oil formulation of Beauveria bassiana were observed. While Metarhizium sp recorded LT50 of 9.0 days and 2.8 days for 103 and 107 spores/ml, respectively. The results obtained were discussed in relation to use of the isolates in the control Z. variegates infestation in forest agro-ecosystem of south west, Nigeria. Key Words: Microbial control, entomopathogenic fungi, Beauveria bassiana, Zonoccrus variegatus, Metarhizium sp. African Journal of Biotechnology Vol.4(1) 2005:113-11

Inhibition of aflatoxin-producing aspergilli by lactic acid bacteria isolates from indigenously fermented cereal gruels

A total of six lactic acid bacteria (LAB) isolates were selected from five indigenously fermented cereal gruels and identified as Lactobacillus fermentum OYB, Lb. fermentum RS2, Lb. plantarum MW, Lb. plantarum YO, Lb. brevis WS3, and Lactococcus spp. RS3. Six aflatoxin-producing aspergilli were alsoselected from the various food sources. Two of the isolates, identified as Aspergillus parasiticus C2 and A. parasiticus AF7, produced both aflatoxin B1 and G while the other four identified as A. flavus M1, A. flavus B4, A flavus B5 and A. flavus C6, produced only aflatoxin B1. Each of the LAB isolatesinhibited the growth of at least a toxin-producing Aspergillus. The maximum inhibitions were shown by Lb. plantarum YO, which was able to inhibit the vegetative and sporulative growth of all the aflatoxinproducing aspergilli. Lactococcus spp. RS3 and Lb. brevis WS3 were only able to inhibit A. parasiticusC7 reasonably and A. flavus B5 and C6 mildly