Conversion of renewable substrates for biosurfactant production by Rhizopus arrhizus UCP 1607 and enhancing the removal of diesel oil from marine soil

BACKGROUND: The use of agro-industrial wastes to produce high value-added biomolecules such as biosurfactants is a promising approach for lowering the total costs of production. This study aimed to produce biosurfactants using Rhizopus arrhizus UCP 1607, with crude glycerol (CG) and corn steep liquor (CSL) as substrates. In addition, the biomolecule was characterized, and its efficiency in removing petroderivatives from marine soil was investigated. RESULTS: A 22 factorial design was applied, and the best condition for producing the biosurfactant was determined in assay 4 (3% CG and 5% CSL). The biosurfactant reduced the surface tension of water from 72 to 28.8 mN/m and produced a yield of 1.74 g/L. The preliminary biochemical characterization showed that the biosurfactant consisted of proteins (38.0%), carbohydrates (35.4%), and lipids (5.5%). The compounds presented an anionic character, nontoxicity, and great stability for all conditions tested. The biomolecule displayed great ability in dispersing hydrophobic substrates in water, thereby resulting in 53.4 cm2 ODA. The best efficiency of the biosurfactant in removing the pollutant diesel oil from marine soil was 79.4%. CONCLUSIONS: This study demonstrated the ability of R. arrhizus UCP1607 to produce a low-cost biosurfactant characterized as a glycoprotein and its potential use in the bioremediation of the hydrophobic diesel oil pollutant in marine soil

Bioconversion of waste cooking oil glycerol from cabbage extract to lactic acid by Rhizopus microsporus

Abstract Glycerol from spent oil was processed by transesterification for biodiesel production. Although glycerol contains many types of impurities, it can be used as a C-source for lactic acid production by fungi, such as Rhizopus microsporus. In this study, we found that wild type R. microsporus (LTH23) produced more lactic acid than the mutant strains on cabbage glycerol media (CG media). More lactic acid was produced on CG media than on cabbage extract media (C media) by about two-fold in batch fermentation conditions. In addition, we found that lactic acid production in a fed-batch process was also slightly higher than in a batch process. To study the combined effects of pH, urea, and glycerol waste concentration on lactic acid production, a response surface methodology was used. The optimum pH, urea, and glycerol waste concentrations were pH 6.5, 3.75 g/L, and 17 g/L, respectively. The maximum lactic acid production predicted by this equation model was 4.03 g/L.

Production of flavor compounds from olive mill waste by Rhizopus oryzae and Candida tropicalis

Abstract The purpose of this study was to investigate the production of flavor compounds from olive mill waste by microbial fermentation of Rhizopus oryzae and Candida tropicalis. Olive mill waste fermentations were performed in shake and bioreactor cultures. Production of flavor compounds from olive mill waste was followed by Gas Chromatography–Mass spectrometry, Gas chromatography- olfactometry and Spectrum Sensory Analysis ®. As a result, 1.73-log and 3.23-log cfu/mL increases were observed in the microbial populations of R. oryzae and C. tropicalis during shake cultures, respectively. C. tropicalis can produce a higher concentration of d-limonene from olive mill waste than R. oryzae in shake cultures. The concentration of d-limonene was determined as 185.56 and 249.54 µg/kg in the fermented olive mill waste by R. oryzae and C. tropicalis in shake cultures respectively. In contrast, R. oryzae can produce a higher concentration of d-limonene (87.73 µg/kg) d-limonene than C. tropicalis (11.95 µg/kg) in bioreactor cultures. Based on sensory analysis, unripe olive, wet towel, sweet aromatic, fermented aromas were determined at high intensity in olive mill waste fermented with R. oryzae meanwhile olive mill waste fermented with C. tropicalis had only a high intensity of unripe olive and oily aroma.

Response of fungal community in the unpolluted and polluted (textile and distillery wastes) habitats.

37 fungal species were recorded, maximum found in textile wastewater polluted habitats (35) followed by unpolluted (15) and distillery polluted (6) habitats. Fungal diversity in sediment samples of textile wastewater polluted habitats (25) was a little lower than wastewater samples (32), whereas it varied little both in the samples of unpolluted habitats (Sambhar wetlands: 5-6; Garden tanks: 9-10) and distillery waste (3-5). Seasonal variation in species diversity was more pronounced in the textile wastewater polluted habitats. Their minimum number was often found during the rainy season while maximum in the winter season, in the polluted habitats but during summer in the unpolluted habitats. Aspergillus was the most diverse genus represented by 7 species, followed by Cladosporium and Fusarium (3 species each) while Drechslera, Rhizopus and Trichoderma had 2 species each. The remaining genera (18) were monotypic. Colony Forming Units (CFUs) were also maximum in the textile wastewater polluted habitats (5.6-1898.9 x 10(3)/L), followed by unpolluted (6.7-560.0 x 10(3)/L) and distillery waste polluted habitats (3.1-53.3 x 10(3)/L), being usually higher in the sediment samples. Their number also varied seasonally, being maximum during winter season in the water samples, whereas in summer in the sediment samples. Aspergillus fumigatus, A. niger, Cladosporium cladosporioides, C. sphaerospermum and Penicillium chrysogenum usually contributed maximum to the CFU values in the polluted as well as in unpolluted habitats.

Extracellular amylase(s) production by fungi Botryodiplodia theobromae and Rhizopus oryzae grown on cassava starch residue.

The fungi Botryodiplodia theobromae and Rhizopus oryzae produce extracellular amylase when grown on a liquid medium containing 2% (WN) soluble starch or cassava starch residue(CSR) (as starch equivalent), a waste generated after extraction of starch from cassava, as the sole carbon source. Using CSR as the sole carbon source, the highest amylase activity of 3.25 and 3.8 units (mg, glucose released x ml(-1) x h(-1)) were obtained in shake flask cultures during the late stationary phase of growth of B. theobromae and R. oryzae, respectively. These values were slightly lower than the values obtained using soluble starch as the carbon source. Maximum enzyme synthesis in CSR incorporated medium occurred at the growth temperature of 30 degrees C and pH 6.0. Presence of inorganic NH4+ salts like ammonium acetate and ammonium nitrate in culture medium yielded more amylase than the other nitrogen sources. Amylase(s) production in the controlled environment of a Table-Top glass Jar Fermenter (2-L capacity) was 4.8 and 5.1 units for B. theobromae and R. oryzae, respectively using CSR as the carbon substrate. It is concluded that CSR, a cheap agricultural waste obtained after starch extraction from cassava could replace soluble starch as carbon substrate for commercial production of fungal amylase(s).

Bioleaching of copper from chalcopyrite ore by fungi.

Microorganisms have been geologically active in mineral formation, mineral diagenesis and sedimentation via direct action of their enzymes or indirectly through chemical action of their metabolic products. This property of microorganisms is being harnessed during the recent years for extraction of metals from their ores, especially from low-grade ores. In the present study bioleaching of copper from its low-grade chalcopyrite ore using 26 isolates of acidophilic fungi is reported. Most of these fungal strains belonged to the genera Aspergillus, Penicillium and Rhizopus. The leaching experiments were conducted in Czepek Dox minimal medium containing 1% (100 mesh) ore with shaking at room temperature for 20 days. Out of these, 4 isolates exhibited significant bioleaching activities. Maximum leaching of copper (78 mg/L) was observed with Aspergillus flavus (DSF-8) and Aspergillus niger (DOF-1). Nutritional and environmental conditions for optimum bioleaching were standardized. Present study indicates the usefulness of acidophilic fungi in bioleaching of copper from its low-grade ores.