Elevated levels of laccase synthesis by Pleurotus pulmonarius BPSM10 and its potential as a dye decolorizing agent.

Laccases (EC 1.10.3.2) are a class of multi-copper oxidases that have industrial value. In the present study, forty-five isolates of wild mushrooms were screened for laccase production. Eight of the isolates exhibited exploitable levels of substrate oxidation capacity. Isolate BPSM10 exhibited the highest laccase activity of 103.50 U/ml. Internal Transcribed Spacer (ITS) rRNA gene sequencing was used to identify BPSM10 as Pleurotus pulmonarius. The response of BPSM10 to two nutritional media supplemented with various inducers was characterized and the results indicated that Malt Extract Broth (MEB) supplemented with Xylidine increased laccase production by 2.8× (349.5 U/ml) relative to the control (122 U/ml), while Potato Dextrose Broth (PDB) supplemented with xylidine increased laccase production by 1.9× (286 U/ml). BPSM10 has the ability to decolorize seven synthetic dyes in a liquid medium. Maximum decolorization was observed of malachite green (MG); exhibiting 68.6% decolorization at 100 mg/L. Fourier-transform infrared spectroscopy (FTIR) was employed to confirm the decolorization capacity. The present study indicates that P. pulmonarius BPSM10 has the potential to be used as a potent alternative biosorbent for the removal of synthetic dyes from aqueous solutions, especially in the detoxification of polluted water.

Utilisation of potato processing wastewater for microbial lipids and γ-linolenic acid production by oleaginous fungi.

BACKGROUND: Microbial lipids are considered as the starting material for production of second-generation biofuels and their polyunsaturated fatty acids are rich sources of neutraceuticals. Exploring cheap feedstock for producing microbial lipids is necessary. The present study examined the potential of microbial lipids and γ-linolenic acid (GLA) production by two oleaginous fungi, Aspergillus flavus I16-3 and Mucor rouxii, with potato processing wastewater as a low-cost or no-cost nutrient source. RESULTS: Biochemistry and physiology of two oleaginous fungi, A. flavus I16-3 and M. rouxii, on lipid accumulation showed the two fungi grew well and efficiently utilised the starch in wastewater. On average (P < 0.05), 2.8 and 3.6 g L(-1) of lipids were produced by A. flavus I16-3 and M. rouxii, respectively, with maximum GLA yields of 60 and 100 mg L(-1) . Addition of nutrients to raw wastewater significantly improved (P < 0.05) the lipid and GLA yields; 3.5 and 4.2 g L(-1) of lipids, and 100 and 140 mg L(-1) of GLA were produced by A. flavus I16-3 and M. rouxii, respectively. In addition, the wastewater was efficiently treated, with soluble chemical oxygen demand, total soluble nitrogen and total soluble phosphorus removals up to 60% and 90%, 100% and 98%, and 92% and 81% by A. flavus I16-3 and M. rouxii, respectively. CONCLUSION: This study demonstrated an alternative approach to valorise potato processing wastewater to produce microbial lipids and GLA (nutraceuticals).

Microbial lipid production from potato processing wastewater using oleaginous filamentous fungi Aspergillus oryzae.

Use of potato processing wastewater for microbial lipid production by oleaginous filamentous fungus Aspergillus oryzae was studied with the purpose of recycling potato processing wastewater for biodiesel production. The wastewater contained high concentrations of solids, starch and nutrients. Sterilization of the potato processing wastewater resulted in a thick gelatinized medium, causing the fungi to grow slow. In order to overcome this problem, the wastewater was diluted with tap water at three dilution ratios (25%, 50% and 75% before fermentation). Dilution of the wastewater not only enhanced lipid production, starch utilization and amylase secretion but also COD and nutrient removal. The dilution ratio of 25% was found to be optimum for lipid production and the maximum lipid concentration obtained was 3.5 g/L. Lipid accumulation was influenced by amylase secretion, and the amylase activity was up to 53.5 IU/mL at 25% dilution. The results show that phosphate limitation may be the mechanism to stimulate the lipid accumulation. In addition to lipid production, removals of COD, total soluble nitrogen and total soluble phosphorus up to 91%, 98% and 97% were achieved, respectively. Microbial lipids of A. oryzae contained major fatty acids such as palmitic acid (11.6%), palmitolic acid (15.6%), stearic acid (19.3%), oleic acid (30.3%), linolenic acid (5.5%) and linoleic acid (6.5%) suggesting that the lipids be suitable for second generation biodiesel production.