Induction characteristics and optimization of production conditions of Xylanase by selected fungal species on lignocellulosic substrates

Five xylanolytic fungi were isolated from saw dust samples collected from a saw mill dump in Ibadan, Nigeria. The effect of lignocellulosic substrates on the production of xylanases was studied in shake flasks. Trichoderma sp. Fd4 produced high yield of the enzyme when grown in 2% wheat bran. Similarly, xylan, lactose and maltose, used as carbon sources induced the production of high levels of xylanase. Trichoderma viride Fd18 produced 10.4 U/ml of xylanase using NH4Cl as nitrogen source, while NH4NO3 repressed enzyme production by Aspergillus ustus Fb2. The fungal isolates produced good amount of xylanase at 30-40 oC, pH 4.5-6.0, 7 days of incubation, initial spore size of 106 and in presence of NaCl and KCl in the basal medium.Keywords: Xylanase, fungi, lignocellulosic waste, submerged fermentation, optimizatio

Production of a Thermostable Α-Amylase and its Assay using Bacillus Licheniformis Isolated from Excavated Land Sites in Ibadan, Nigeria

Screening for amylolytic properties from obtained isolates was carried out on starch agar plates while production and characterization of α-amylase was carried out using submerged fermentation. The isolated organism was identified as Bacillus licheniformis. Physiological studies on the isolate showed that temperature of 55ºC and pH 7 was optimum for growth of the organism while fructose (1%), peptone (0.5%), pH 7 and temperature of 60ºC supported optimum amylase production. Crude characterization of α-amylase revealed optimum amylolytic activity at pH 7 and a temperature of 70ºC. The isolated Bacillus licheniformis produced thermostable α-amylase with characteristics suitable for use in starch processing other industries

Time related total lactic acid bacteria population diversity and dominance in cowpea-fortified fermented cereal-weaning food

The total lactic acid bacterial community involved in the spontaneous fermentation of malted cowpea fortified cereal weaning food was  investigated by phenotypically and cultivation independent method. A total of 74 out of the isolated 178 strains were Lactobacillus plantarum, 32 were Pediococcus acidilactici and over 60% were Lactobacillus strains. L. plantarum and P. acidilactici strains were the dominant strains during the fermentation process and were identified in all the three cereals used.Separation of amplified V3 region from 16S rDNA by denaturing gradient gel electrophoresis (DGGE) using species, specific primer was carried out. The results show that the total lactic acid bacterial species richness (R) decreased with increase in fermentation time, while the species diversity and dominance indices were not significantly (P < 0.05) affected by fermentation time but rather by cerealtype. Comparison of 16S rDNA sequences of pure culture isolates with those in Genbank database revealed that, the dominating lactic acid bacteria were L. plantarum and Pediococcus species.Key words: Lactic acid bacteria, communities’ diversity, fortified weaning foods, polymerase chain reaction amplification-denaturing gradient gel electrophoresis (DGGE)

Partial Purification and Characterization of Extracellular Protease from Pedicoccus acidilactici

Microbial proteases have wide industrial applications and proteases of the lactic acid bacteria (LAB) have received special attention because of their importance in the food and dairy industry. Of all the LAB, the proteolytic system of the pediococci is the least studied. Therefore, this study was aimed at characterizing and purifying the protease produced by Pediococcus acidilactici grown in de Man, Rogosa and Sharpe (MRS) broth. Casein concentration of 2% (w/v) and 2.5 ml of the crude enzyme were optimal for the activity of the protease. The crude protease had temperature and pH optima of 28 oC and 4.0 respectively thus indicating that the enzyme is a mesophilic and acidic protease. Purification of the enzyme by gel filtration chromatography on Sephadex G75 following ammonium sulphate precipitation gave 2.26 fold increase in purification with specific activity of 46.13 units/mg protein while purification on Sephadex CM50 resulted in reduced purification fold (1.24 - 1.59) with specific activity ranging between 25.39 - 32.54 units/mg protein. The protease showed a characteristic band on SDS-PAGE and the molecular weight was estimated between 45 and 66 kDa. The potential applications of the protease are discussed.Keywords: Protease, lactic acid bacteria, Pediococcus acidilactici, enzyme purification

Effect of varying relative humidity on the rancidity of cashew (Anacardium occidentale L.) kernel oil by lipolytic organisms

Post harvest deterioration by microbes due to improper storage condition is considered to be the major cause of spoilage and rancidity of most oil-bearing seeds like cashew nuts through lipolytic action of lipase enzyme. Roasted cashew nuts were subjected to four different storage conditions with different relative humidity of 30, 70, 80 and 90%, respectively for a period of twelve days. Oil extracted from cashew kernel at each storage condition was examined for rancidity. Eight fungal species and three bacteria were obtained and identified as Aspergillus niger, Rhizopus sp., Penicillium sp., Trichoderma sp., Botryodiplodia sp., Fusarium sp., Aspergillus flavus and Aspergillus ochraceous while the bacteria isolates were identified as Bacillus subtilis, Bacillus licheniformis and Staphylococcus sp., respectively. Rancidity of extracted cashew oil was observed with cashew kernel stored at 70, 80 and 90% of relative humidity with increase in time while no level of rancidity was detected at 30% of relative humidity judging by the peroxide value, free fatty acid value, specific gravity and acid value of the oil. Isolates with the highest frequency of occurrence were found to be A. niger and Rhizopus sp. for fungal and B. subtilis and B. licheniformis for the bacterial isolates. These four isolates were screened for conditions for optimal growth and lipolytic activities in a chemically defined medium. Result of the assay shows that lipase enzyme produced by A. niger had the highest lipolytic activity at 37°C.Key words: Cashew kernel, storage conditions, rancidity, lipolytic

Quality characteristics of bread produced from composite flours of wheat, plantain and soybeans

The use of soy flour (SF) and plantain flour (PF) substitution in wheat flour (WF), from 0 to 15% each, for the production of bread was investigated. The proximate analysis, sensory evaluation and aerobic plate count (APC) of the bread samples were determined. The crude protein, crude fiber, ether extract and ash contents of the soy supplemented breads (SSBs) increased with progressive increase in the proportion of soy flour, with the 15% SSB having highest values of 8.39, 0.14, 2.46 and 1.17%, respectively, while lowest values were recorded for the whole wheat bread (WWB). The carbohydrate content was observed to decrease with corresponding increase in the percentage of soy flour in SSBs. The sensory evaluation shows that no significant differences were observed between the WWB and the 5% SSB in the sensory attributes of aroma, internal texture, taste and general acceptability (

PCR-DGGE fingerprints of microbial successional changes during fermentation of cereal-legume weaning foods

Phenotypic identification and monitoring of the dynamics of naturally occurring microbial community responsible for the spontaneous fermentation of different cereal-legume weaning blends was carriedout. Enumeration using culture-dependent method showed that cell counts increased within the first 24 h with the highest total viable count of 1.2 x 1012 cfu g-1 in maize-legume (1A) blend. Yeast countsincreased drastically and no enterobacteria were observed within the first 24 h. At all fermentation times, acidity increased within 48 h and lowest pH value (3.60) was reached in maize–based blend. Phenotypic identification revealed that the isolated bacteria belong to the genera Bacillus species, Staphylococcus aureus, and Escherichia coli. The yeast isolates were identified as Saccharomyces cerevisiae, Saccharomyces species and Hansenula species while Lactobacillus plantarum and Pediococcus acidilactici were the predominant lactic acid bacteria (LAB). The analysis of the denaturing gradient gel electrophoresis (DGGE) pattern obtained with bacterial and LAB primers targeting the V3 region of the 16S rDNA genes clearly demonstrated that there was a major shift in the communitystructure within the first 24 h

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

Detection of fungi and aflatoxin in shelved bush mango seeds (

A survey of the fungi and aflatoxin contamination of bush mango seeds (Irvingia spp.) was conducted in Akwa lbom State, Nigeria. Bush mango seeds sold at four major markets, located at Abak, Uyo, IkotEkpene and Itam in Akwa Ibom State were heavily contaminated with moulds. Eight different fungi were found associated with the bush mango seeds; Aspergillus carbonarius, Aspergillus tereus, Aspergillusflavus, Aspergillus candidus, Penicillium expansum, Aspergillus niger, Candida tropicalis and Aspergillus glaucus. A. niger have the highest rate of occurrence with high colony counts (1.0 x 103 –4.3 x 103 colonies/g). The aflatoxins B1 and G1 concentrations ranged from 0.2 – 4.0 and 0.3 – 4.2 ìg/kg, respectively. The result showed that bush mango seeds sold in Akwa lbom markets require quality control and proper preservation

Reduction of oligosaccharide content of soybeans by the action of Lactobacillus plantarum isolated from fermented cereals

Most African foods used in weaning are usually fermented cereals which supplies mainly carbohydrate. Unless these are supplemented with other nutrient sources, they may lead to excessive intake of carbohydrate which might cause malnutrition in growing children. Minimum dietary requirements of a child for protein could be met through fortification with legumes like cowpea, peanuts or soybeans but they contain raffinose family of oligosaccharide (RFOs), which are responsible for gas formation, bloating and flatulence in children. This work aims at using Lactobacillus plantarum and the enzyme α- and β-galactosidases it produces, to hydrolyse raffinose to simple sugars and hence improve the raffinose-containing weaning foods. Three strains of L. plantarum obtained from fermented cereal gruels and identified using both classical and molecular methods were selected after screening for their ability to produce these enzymes in abundance. They were used to ferment different combinations of cereals and legumes. The oligosaccharide profile before and after the various pre-treatment methods and fermentation were determined using gas chromatography with flame ionization detector (GC-FID). Data obtained were analysed using ANOVA at p < 0.05. Fermentation for 120 h with L. plantarum reduced the total RFO content of soybeans to different levels in the samples. Losses of 30, 28 and 37% in stachyose, raffinose and verbascose, respectively were observed in the fermented raw samples; 72, 58 and 41% reduction in the fermented cooked samples and 76, 68 and 71% reduction in the roasted samples relative to the untreated samples. The use of galactosidase enzymes by L. plantarum from fermented cereals reduced the raffinose-oligosaccharide profile with simultaneous increase in reducing sugar levels. Adequate weaning foods can be prepared with such and the problem of bloating, gas production and flatulence can be solved by the action of L. plantarum in legume-cereal blends.Keywords: Raffinose-oligosaccharides, soybeans, fermented cereals, Lactobacillus plantarum, alpha-galactosidase, weaning foodsAfrican Journal of Biotechnology, Vol 13(37) 3790-379