Waste peels as low cost substrate for microalgal cultivation under a biorefinery approach

Abstract

quotThe potent utilization of cheap and renewable biomass for the production of fuels and value-added bio products is important for addressing the problems related to fossil fuel depletion. Microalgae has emerged as an excellent resource in this regard but the excessive cost of nutrients is a vital restriction for producing economically viable algal fuels. Substitution of the chemical growth medium of microalgae with low cost organic biomass such as food or agricultural waste substrate could help in dealing the cost related problems associated with cultivation of microalgae and also in dealing with heaps of agricultural and food waste generated daily. The suitability of potato, banana and sweet lime peel hydrolysate were evaluated for microalgae cultivation. Different pre-treatment processes were carried out for all the three peels and the best conditions yielding higher amount of glucose concentration were further hydrolyzed by enzyme. Response surface methodology (RSM) was used to optimize the hydrolysis conditions to attain high glucose concentration. The three parameters chosen for the study were; time (h), temperature (oC) and the rotation frequency or agitation speed of the incubator (revolutions per minute i.e. RPM). 46.17 ±0.77 g L-1, 29.84 ± 0.57 g L-1 and 35.90 ±0.43 g L-1 of glucose yield were obtained for potato, banana and sweet lime peels respectively under optimum conditions. The waste peels were further characterized through proximate and ultimate analysis, compositional analysis, FESEM, EDX, FTIR and pH study. Two indigenous microalgae strains Chlorella sorokiniana KMBM_I (Strain I ) and Chlorella sorokiniana KMBM_K (Strain K ) were tested for their growth and adaptability in the peel wastes. Growth kinetic parameters of the strains were analyzed in varying culture conditions. A new insight can be obtained with this study as it integrates the concept of lipid extracted microalgal biomass residue utilization (LEMBR) approach along with waste disposal thereby serving in the management of these waste