Pretreatment of algal biomass using fungal crude enzymes
Graphical abstract
Introduction
Algae are being projected as a major contributor in the biomass feedstock for renewable energy generation in the coming future. The common biofuels produced from algal biomass are biohydrogen, biomethane, biodiesel and bioethanol [1], [2], [3]. Biomethane production through anaerobic digestion of algal biomass is gaining much interest due to minimal processing required in this route [4]. However, pretreatment of algal biomass prior to its use in biofuel generation (including biomethane) is necessary to achieve significant fuel production. Several attempts have been made on pretreatment of algal biomass to improve its biofuel productivity. The major pretreatment methods available till date are either mechanical or chemical. These methods significantly improve the biofuel production from algae [5] but are highly energy as well as capital intensive which eventually makes algal biofuel uneconomical and unviable at a commercial scale.
It is well known that most of the unicellular algae possess cell wall composed of cellulose, hemicellulose/xylan and chitin [6], [7]. Enzymes can be used as a pretreatment agent for algal cell disruption. However, enzymes are highly specific and algal cell walls are made up of complex biopolymers. Therefore, rather than a single enzyme, an enzyme cocktail is needed to hydrolyze target microalgal species efficiently [8]. There have been some attempts on algal biomass pretreatment using commercial enzymes including a-amylase, amyloglucosidase [9] and cellulase, xylanase, lipase, and protease [8]. However, use of commercial enzyme for algal biomass pretreatment for biofuel production is economically unviable. Furthermore, fungi have unique ability to produce a wide range of extracellular enzyme complexes including cellulase and xylanase [10]. Therefore, fungal crude enzymes could provide a cheaper alternative for commercial enzyme for pretreating algal biomass. To the best of our knowledge, no previous report is available on fungal crude enzyme based pretreatment methods for algal biomass.
Hence, in the light of the above discussion, the present work was focused on exploring the application potential of fungal crude enzymes for algal biomass pretreatment.
Section snippets
Microbial strains and substrates
Two fungal strains, Aspergillus lentulus and Rhizopus oryzae, previously isolated from environmental samples (textile effluent collected from Baddi, Himachal Pradesh and dumping site in IIT Delhi, respectively) and reported to produce enzymes with good cellulase and xylanase activity [11] were used for production of crude enzymes. The fungal cultures were maintained on a potato dextrose agar at 4 °C and revived routinely. Freshly revived cultures (incubated for 3 d) were used throughout the
Characterization of crude enzyme
The fungal crude enzymes were characterised on the basis of total protein content and cellulase and xylanase activities. The total protein content (mg mL− 1), cellulase activity (FPU mL− 1) and xylanase activity (IU mL− 1) of the crude enzymes obtained from A. lentulus and R. oryzae under SSF were 4.005, 0.169 and 0.658 and, 4.760, 0.102 and 0.935, respectively. Hence, A. lentulus has approximately 1.6 times cellulase activity compared to that observed with R. oryzae grown on ScB. However, the
Conclusion
The present report is a pioneering attempt in the direction of algal biomass pretreatment employing fungal crude enzymes. Good levels of fungal crude enzyme were produced utilizing agricultural residues (sugarcane bagasse) under solid state fermentation. Among the tested fungi, A. lentulus was found to produce crude enzymes with relatively higher cellulase activity. Interestingly, the crude enzyme produced by A. lentulus showed good pretreatment (at a loading equivalent to ≈ 21.125 FPU g− 1 algal
Acknowledgments
The present work was carried out with financial support received under R&D project sponsored by Science and Engineering Research Board (SERB), Department of Science and Technology, Government of India (SB/S3/CEE/0002/2014). Mr. Pushpendar and Ms. Poonam Choudhary, PhD Scholar, CRDT, IIT Delhi are acknowledged for their technical assistance during the present work. The authors appreciate the assistance provided by Mr. Vinod Kumar and Mr. Vikarm Singh (Project staff, IIT Delhi).
References (31)
- et al.
Phycoremediation coupled production of algal biomass, harvesting and anaerobic digestion: possibilities and challenges
Biotechnol. Adv.
(2013) - et al.
Anaerobic digestion of microalgae as a necessary step to make microalgal biodiesel sustainable
Biotechnol. Adv.
(2009) - et al.
Microalgae as substrates for fermentative biogas production in a combined biorefinery concept
J. Biotechnol.
(2010) - et al.
Influence of different pre-treatment routes on the anaerobic digestion of a filamentous algae
Renew. Energy
(2013) - et al.
Enzymatic pretreatment of Chlamydomonas reinhardtii biomass for ethanol production
Bioresour. Technol.
(2010) - et al.
Phycoremediation and biogas potential of native algal isolates from soil and wastewater
Bioresour. Technol.
(2013) - et al.
Algae mediated treatment and bioenergy generation process for handling liquid and solid waste from dairy cattle farm
Bioresour. Technol.
(2014) - et al.
Bioconversion of algae to methane and subsequent utilization of digestate for algae cultivation: a closed loop bioenergy generation process
Bioresour. Technol.
(2014) - et al.
A novel method for kinetic measurements of rare cell proliferation using cellometer image-based cytometry
J. Immunol. Methods
(2012) - et al.
Interlaboratory testing of methods for assay of xylanase activity
J. Biotechnol.
(1992)
Protein measurement with the folin phenol reagent
J. Biol. Chem.
In situ sem, tem and afm studies of the antimicrobial activity of lemon grass oil in liquid and vapour phase against Candida albicans
Micron
A novel method to harvest microalgae via co-culture of filamentous fungi to form cell pellets
Bioresour. Technol.
Enhancement of fermentative hydrogen production from green algal biomass of thermotoga neapolitana by various pretreatment methods
Int. J. Hydrogen Energy
Biochemical methane potential of microalgae: influence of substrate to inoculum ratio, biomass concentration and pretreatment
Bioresour. Technol.
Cited by (62)
Biological pretreatment for algal biomass feedstock for biofuel production
2023, Journal of Environmental Chemical EngineeringClosed loop bioeconomy opportunities through the integration of microalgae cultivation with anaerobic digestion: A critical review
2023, Bioresource Technology ReportsAlgae cultivation in industrial effluents for carbon dioxide sequestration and biofuel production
2023, Valorization of Wastes for Sustainable Development: Waste to Wealth