Potential role of N-acetyl glucosamine in Aspergillus fumigatus-assisted Chlorella pyrenoidosa harvesting

Abstract

Background Algal harvesting is a major cost which increases biofuel production cost. Algal biofuels are widely studied as third-generation biofuel. However, they are yet not viable because of its high production cost which is majorly contributed by energy-intensive biomass harvesting techniques. Biological harvesting method like fungal-assisted harvesting of microalgae is highly efficient but poses a challenge due to its slow kinetics and poorly understood mechanism. Results In this study, we investigate Aspergillus fumigatus – Chlorella pyrenoidosa attachment resulting in a harvesting efficiency of 90% within 4 h. To pinpoint the role of extracellular metabolite, several experiments were performed by eliminating the C. pyrenoidosa or A. fumigatus spent medium from the C. pyrenoidosa – A. fumigatus mixture. In the absence of A. fumigatus spent medium, the harvesting efficiency dropped to 20% compared to > 90% in the control, which was regained after addition of A. fumigatus spent medium. Different treatments of A. fumigatus spent medium showed drop in harvesting efficiency after periodate treatment (≤ 20%) and methanol–chloroform extraction (≤ 20%), indicating the role of sugar-like moiety. HR-LC–MS (high-resolution liquid chromatography–mass spectrometry) results confirmed the presence of N -acetyl- d -glucosamine (GlcNAc) and glucose in the spent medium. When GlcNAc was used as a replacement of A. fumigatus spent medium for harvesting studies, the harvesting process was significantly faster ( p < 0.05) till 4 h compared to that with glucose. Further experiments indicated that metabolically active A. fumigatus produced GlcNAc from glucose. Concanavalin A staining and FTIR (Fourier transform infrared spectroscopy) analysis of A. fumigatus spent medium- as well as GlcNAc-incubated C. pyrenoidosa cells suggested the presence of GlcNAc on its cell surface indicated by dark red dots and GlcNAc-specific peaks, while no such characteristic dots or peaks were observed in normal C. pyrenoidosa cells. HR-TEM (High-resolution Transmission electron microscopy) showed the formation of serrated edges on the C. pyrenoidosa cell surface after treatment with A. fumigatus spent medium or GlcNAc, while Atomic force microscopy (AFM) showed an increase in roughness of the C. pyrenoidosa cells surface upon incubation with A. fumigatus spent medium. Conclusions Results strongly suggest that GlcNAc prese...

Efficient Strategy by a Newly Isolated Aspergillus oryzae to Harvest Chlorella vulgaris MBFJNU-1 from Original Swine Wastewater

“…Samples containing fungal pellets, microalgal cells, and fungal–microalgal pellets were first fixed with 2.5% glutaraldehyde solution at 4 °C . These samples were coated with gold and then observed by a scanning electron microscope (SEM, SU8020, Hitachi Science systems, Ltd., Tokyo, Japan).…”

A comparative analysis of algal biomass densification methods aimed at the biofuel production

“…One of the most efficient bioflocculation techniques is inoculating fungal pellets into the microalgae suspension to form dense agglomerates that settle quickly [88,89]. Another technique studied is the co-cultivation of bacteria and fungi with the microalgae of interest, which allow the formation of aggregates that settle [90].…”

Cell‐cultivated food production and processing: A review

“…A disadvantage of electroflocculation is relatively high energy costs. Bioflocculation is a flocculation process where other organisms such as fungi (Bhattacharya et al, 2019; Gultom & Hu, 2013), other microalgae (Salim et al, 2011), and/or bacteria (Powell & Hill, 2013) are used to harvest the microalgae. An advantage that bioflocculation has over other methods is that the flocculating organism can be selected to be nontoxic and the growth media can usually be recycled.…”