Saleh M. Al-Garni

Biosorption characteristics of Aspergillus fumigatus in removal of cadmium from an aqueous solution

Nineteen fungal species were isolated from soil contaminated with industrial wastes of which Aspergillus species were the most dominant. The growth of the isolates was notice by Cd concentration in growth medium, thus about 20% of the isolates can grow up to 50 mg Cd/100 ml medium and only Aspergillus fumigatus and Penicillium chrysogenum can grow at 100 mg Cd with growth decrease of 88.2 and 99.4%, respectively. The results revealed that the living biomass of the isolates were more efficient to biosorb Cd than their dried powdered biomass by 15 - 44%. The formulation of yeast peptone glucose (YPG) medium fortified the isolates by ingredients favored the best growth yields that have the highest Cd biosorption, compared to yeast malt extract (YM) and sabourad (Sb) media. The dried A. fumigatus biomass was the most efficient than other tested fungi. The influence of different treatments of dried A. fumigatus biomass on its Cd biosorption activity, indicated that 0.5 N NaOH and autoclaving was the most efficient treatment (3 fold increase as compared to untreated). The biosorption of Cd by treated A. fumigatus biomass was considerably influenced by the pH value of the biosorption medium, contact time, biomass levels and Cd concentration. Thus, 98% of Cd was absorbed in biosorption medium containing 10 mg Cd and 100 mg dried treated biomass/100ml bidistilled water at pH 5 after 90 min of contact, nitric acid (0.05 N) was the best Cd eluent (99.8%) as compared to the other eluents. The desorbed A. fumigatus biomass was successfully reused for 5 consecutive times for Cd biosorption with decrease reached to 28% at the 5th reuse.

Solid state production of polygalacturonase and xylanase by Trichoderma species using cantaloupe and watermelon rinds

Different solid state fermentation (SSF) sources were tested such as cantaloupe and watermelon rinds, orange and banana peels, for the production of polygalacturonase (PG) and xylanase (Xyl) by Trichoderma harzianum and Trichoderma virens. The maximum production of both PG and Xyl were obtained by T. harzianum and T. virnes grown on cantaloupe and watermelon rinds, respectively. Time course, moisture content, temperature, pH, supplementation with carbon and nitrogen sources were optimized to achieve the maximum production of both PG and Xyl of T. harzianum and T. virens using cantaloupe and watermelon rinds, respectively. The maximum production of PG and Xyl of T. harzianum and T. virens was recorded at 4–5 days of incubation, 50–66% moisture, temperature 28–35°C and pH 6–7. The influence of supplementary carbon and nitrogen sources was studied. For T. harzianum, lactose enhanced PG activity from 87 to 120 units/g solid, where starch and maltose enhanced Xyl activity from 40 to 55–60 units/g solid for T. virnes. Among the nitrogen sources, ammonium sulphate, ammonium nitrate, yeast extract and urea increased PG activity from 90 to 110–113 units/g solid for T. harzianum. Similarly, ammonium chloride, ammonium sulphate and yeast extract increased Xyl activity from 45 to 55–70 units/g solid for T. virens.

Efficient production of lycopene in Saccharomyces cerevisiae by expression of synthetic crt genes from a plasmid harboring the ADH2 promoter

Lycopene is an effective antioxidant proposed as a possible treatment for some cancers and other degenerative human conditions. This study aims at generation of a yeast strain (Saccharomyces cerevisiae) of efficient productivity of lycopene by overexpressing synthetic genes derived from crtE, crtB and crtI genes of Erwinia uredovora. These synthetic genes were constructed in accordance with the preferred codon usage in S. cerevisiae but with no changes in amino acid sequences of the gene products. S. cerevisiae cells were transformed with these synthetic crt genes, whose expression was regulated by the ADH2 promoter, which is de-repressed upon glucose depletion. The RT-PCR and Western blotting analyses indicated that the synthetic crt genes were efficiently transcribed and translated in crt-transformed S. cerevisiae cells. The highest level of lycopene in one of the transformed lines was 3.3mglycopene/g dry cell weight, which is higher than the previously reported levels of lycopene in other microorganisms transformed with the three genes. These results suggest the excellence of using the synthetic crt genes and the ADH2 promoter in generation of recombinant S. cerevisiae that produces a high level of lycopene. The level of ergosterol was reversely correlated to that of lycopene in crt-transformed S. cerevisiae cells, suggesting that two pathways for lycopene and ergosterol syntheses compete for the use of farnesyl diphosphate.

Chitinolytic enzyme production and genetic improvement of a new isolate belonging to Streptomyces anulatus

Thirty bacterial isolates were obtained from different sources and sites at Jeddah, Saudi Arabia, on chitin agar medium; 9 of the 30 isolates were cultured in liquid medium containing chitin as sole carbon and nitrogen sources. Isolate SM21, which was isolated from shrimp shells, showed the best growth and chitinase production in liquid medium. According to its morphological, physiological and biochemical characteristics, SM21 belongs to the genus Streptomyces and was identified as Streptomyces anulatus SM21. Identification was confirmed using 16S rDNA analysis. The chitinase enzyme was precipitated with 80% NH4SO4 and purified using DEAE-cellulose ion exchange chromatography followed by Sephadex G-100 gel filtration. The molecular weight determined using sodium dodecyl sulfate polyacrylamide gel electrophoresis was 28 kDa. Genetic improvement using the protoplast fusion technique was carried out between the identified Streptomyces isolate and Streptomyces coelicolor SM1. These two species, which have different resistance profiles to streptomycin and tetracycline (400 μg/ml and 10 μg/ml, respectively), were used in an intraspecific protoplast fusion using PEG 6000. The percentage of real protoplasts that could regenerate successfully was 71% for S. coelicolor SM1 and 80% for S. anulatus SM21. Out of three recombinant fusants obtained, one (named Fu3) showed higher chitinase production compared to both parents (5 fold increase).

Isolation and identification of bacterial consortia responsible for degrading oil spills from the coastal area of Yanbu, Saudi Arabia

ABSTRACT Twenty-three crude-oil-degrading bacteria were isolated from oil-contaminated sites near the Red Sea. Based on a high growth rate on crude oil and on hydrocarbon degradation ability, four strains were selected from the 23 isolated strains for further study. These four strains were selected on the basis of dichlorophenolindophenol assay. The nucleotide sequences of the 16S rRNA gene showed that these isolated strains belonged to genus Pseudomonas and Nitratireductor. Among the four isolates, strains S5 (Pseudomonas sp., 95%) and 4b (Nitratireductor sp., 70%) were the most effective ones in degrading crude oil. Using a spectrophotometer and gas chromatography–mass spectrometry, degradation of more than 90% of the crude oil was observed after two weeks of cultivation in Bushnell–Haas medium. The results showed that these strains have the ability to degrade crude oil and may be used for environmental remediation.

Statistical optimization of cultural conditions for decolorization of methylene blue by mono and mixed bacterial culture techniques

Acinetobacter baumannii, Corynebacterium sp., Cytophaga columnaris, Escherichia coli, Pseudomonas fluorescence and Pseudomonas luteola were locally isolated bacteria from sewage Disposal Lake at Jeddah, Saudi Arabia and they can decolorize methylene blue. E. coli was the most potent MB decolorizing and to a lesser extend P. luteola. Five different media were tested to elucidate medium formulation in favor of MB decolorization by E. coli and P. luteola. Ingredients of the basal medium favored the complete decolorization of 50 μg MB/ml after 84 h of fermentation. Time course decolorization of MB by E. coli indicated that 75 h of fermentation was satisfactory to decolorize 50 μg MB/ml. It was also able to decolorize different levels of MB up to 150 μg MB/ml after 95 h of fermentation. Bacterial consortium of E. coli and P. luteola was highly efficient to decolorize MB than monoculture, where the decolorization period reduced by more than 37% and increased decolorization rate (μgMB/h) up to 58%. Statistical designs of two phase multifactorial optimization (Plackett-Burman and Box-Behnken) were carried out to optimize cultural conditions to increase the efficiency of mixed culture to decolorize 150 μg MB/ml. Under the optimized conditions the decolorization period was reduced by about 31.7% and with increased decolorization rate by 46.4%. Methylene blue can be efficiently decolorized by facultative aerobic bacteria (E. coli and P. luteola). The decolorization process was markedly influenced by the composition of the fermentation medium and concentration of MB. Mixed culture of E. coli and P. luteola was highly efficient to decolorize MB than monoculture technique. The cultural conditions were considerably optimized using statistical experimental designs of PlackettBurman and Box-Behnken.

Mycoflora Associated with Some Textiles in Jeddah City

تم عزل الفطريات المصاحبة لثمانية أنواع مختلفة من المنسوجات ( ألياف طبيعية ، وصناعية وخليط) جمعت من مراكز تسويقية في مدينة جدة بالمملكة العربية السعودية. وقد تم استخدام طرق التلامس ، والتخفيف ، والتجانس، والترطيب في عزل وتقدير أعداد وتعريف الفطريات المصاحبة للمنسوجات.وقد تم الحصول على ثلاث وعشرين عزلة فطرية، شكلت أنواع الأسبر جللس نسبة 35% متبوعة بأنواع البنيسيليا والفيوزاريا بنسبة 13% لكل منها. وقد سجلت أعلى أعداد الفطريات على منسوجات القطن ( حتى عندما كانت مخلوطة) حيث بلغت 1932 مستعمرة لكل سم2. جاءت بعدها منسوجات الصوف، بأعداد بلغت 1421 مستعمرة لكل سم2. وفي حين أظهرت منسوجات الحرير قابلية أقل للإصابة بالفطريات، كانت الأعداد الفطرية في منسوجات البوليستر متوسطة الكثافة. كذلك تم اختبار تأثير بعض الظروف البيئية ( مثل الحرارة والوسط الغذائي ودرجة الحموضة والرطوبة النسبية ) على النمو الفطري لعشر من الفطريات المعزولة المعرفوة بإحداث بعض الأضرار للإنسان وهي Alternaria alternata, Aspergillus flavus, A. fumigatus, A. niger, Fusarium oxysporium, Geotrichum sp., Gliocladium atrum, Penicillium chrysogenum, Rhizopus nigricans, Trichoderma viride ولقد أظهرت دراسة الأنشطة الإنزيمية للسليوليز والبروتييز تفوق T.viride و Geotrichm sp. و A. nger و A. alternate و P. chry- sogemum. كما أوضحت دراسة النشاط التضادي لنوعين من المنظفات التباين في درجة التأثير على الفطريات المختبرة حسب نوع وتركيز المنظف.

Biodegradation of Kerosene by Aspergillus flavus Using Statistical Experimental Designs

ABSTRACT The ability of different local fungal isolates to degrade kerosene in liquid medium was studied. The results showed that the percent of kerosene degradation varied among the different tested fungi and that 60–96% of kerosene was degraded after 7 days in the presence of 0.2% (v/v) of Tween 80. The absence of the surfactant led to about 28.34% decrease of biodegradation. The degradation of 2% (v/v) of kerosene by the most efficient fungus (Aspergillus flavus) was significantly influenced by the incubation period and the composition of culture medium. Statistical experimental designs were used to optimize the process of kerosene degradation by the fungus. Under optimized medium compositions and culture conditions, A. flavus degraded kerosene (100%) after 111.3 h of incubation. Optimal conditions obtained in this work provided a solid foundation for further use of A. flavus in treatment of kerosene-polluted soil. The optimized conditions were applied to bioremediate 2.5% (v/w) kerosene-polluted soil by A. flavus, and the fungus efficiently degraded kerosene after 35 days of incubation.

Application of a five level central composite design to optimize operating conditions for electricity generation in a microbial fuel cell

Abstract In this work, a five level central composite design (Box–Wilson design) was employed to optimize the operating conditions for the generation of electricity in a microbial fuel cell. The following three variables were studied: temperature, initial anodic compartment pH and salt bridge component concentrations (agar and KCl). The optimal voltage yield was 17.34% greater than that observed under basal conditions and was achieved with a temperature of 32 °C, constant pH of 7.0 and salt bridge component concentrations of agar: 8.0 g/100 ml and KCL: 2.9 g/100 ml. The maximum recorded voltage at an external resistance of 30 Ω was 861.27 mV. The current density was 2.16 mA/m2, the power density was 1887.49 mW/m2, and the columbic efficiency was 24.12%.

Solid-state fermentation by Trichoderma viride for enhancing phenolic content, antioxidant and antimicrobial activities in ginger

The phenolic content of methanol and water extracts of ginger fermented by Trichoderma spp. using solid‐state fermentation (SSF) was evaluated and was compared with unfermented ginger. The total phenolic content in fermented ginger increased several times. The highest phenolic content in ginger was detected after SSF by T. viride. The optimal physiological conditions for the maximum production of phenolic compounds and β‐glucosidase activity of fermented ginger by T. viride were detected at day 7 incubation, pH 6·0, 30°C and 30% moisture. The SSF of ginger by T. viride greatly enhanced the antioxidant potency of phenolic compounds and was evaluated using DPPH and ABTS assays. A potent antibacterial activity of the phenolic compounds of fermented ginger was observed against all the tested human‐pathogenic bacteria.