Bioconversion of sago processing wastewater into biodiesel: Optimization of lipid production by an oleaginous yeast, Candida tropicalis ASY2 and its transesterification process using response surface methodology

Abstract

Background Biodiesel is an eco-friendly and renewable energy source and a valuable substitute for petro-diesel. Sago processing wastewater (SWW), a by-product of the cassava processing industry, has starch content ranging from 4 to 7 g L–1 and serves as an outstanding source for producing microbial lipids by the oleaginous microorganisms. In the present study, Candida tropicalis ASY2 was employed to optimize single-cell oil (SCO) production using SWW and subsequent transesterification by response surface methodology. Variables such as starch content, yeast extract, airflow rate, pH, and temperature significantly influenced lipid production in a preliminary study. The lipid production was scaled up to 5 L capacity airlift bioreactor and its optimization was done by response surface methodology. The dried yeast biomass obtained under optimized conditions from 5 L bioreactor was subjected to a direct transesterification process. Biomass: methanol ratio, catalyst concentration, and time were the variables used to attain higher FAME yield in the transesterification optimization process. Results Under optimized conditions, the highest lipid yield of 2.68 g L–1 was obtained with 15.33 g L–1 of starch content, 0.5 g L–1 of yeast extract, and 5.992 L min–1 of airflow rate in a bioreactor. The optimized direct transesterification process yielded a higher FAME yield of 86.56% at 1:20 biomass: methanol ratio, 0.4 M catalyst concentration, and a time of 6.85 h. Conclusions Thus, this optimized process rendered the microbial lipids derived from C. tropicalis ASY2 as potentially alternative oil substitutes for sustainable biodiesel production to meet the rising energy demands.

Special Issue ‘Microbial glycobiotechnology’

“…Microbial glycobiotechnology refers to sustainable bioprocesses for the bioconversion of carbohydrates through microbial enzymes and microbial technologies and the generation of tailor-made carbohydrate bioproducts/polymers for various novel applications in bioenergy and bioenergy fuels, biomaterials, in food and nutrition, and pharmaceuticals.This special issue is intended to present a special collection with a thematic scheme: Microbial Glycobiotechnology. Eighteen articles, connected to glycan biosynthesis, glycoenzymology, modification of complex carbohydrates and their corresponding glycoconjugates, including glycans, glycoproteins, glycolipids, biological functions of glycoconjugates and glycolipids, have been published there [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18].…”

“…In another study, Thangavelu et al [2] investigated the bioconversion potential of Candida tropicalis ASY2 to produce biodiesel from sago processing wastewater (SWW). They observed that the microbial lipids from C. tropicalis strain as alternative oil substitutes for sustainable biodiesel production.…”

“…Author details 1 Centre for Innovation and Translational Research, CSIR-Indian Institute for Toxicology Research (CSIR-IITR), Lucknow 226001, India. 2 Centre for Energy and Environmental Sustainability, Lucknow 226029, Uttar Pradesh, India. 3 Sustainability Cluster, School of Engineering, University of Petroleum and Energy Studies, Dehradun 248007, Uttarkhand, India.…”

Production of sustainable biodiesel from alkaline pretreated dairy effluent using Yarrowia lipolytica

“…MTCC 5455 produces BD from Brassica juncea gives the highest FAME yield of 15% after 10 h of enzymatic reaction 58 . BD was derived from the oleaginous yeast Candida tropicalis ASY2 yielded a higher FAME of 86% at the optimized conditions 59 . Base‐catalyzed such as KOH transesterification is the favored method when compared to the other methods since it has softer reaction conditions, requires less time to complete, and is less expensive 60 .…”

“…58 BD was derived from the oleaginous yeast Candida tropicalis ASY2 yielded a higher FAME of 86% at the optimized conditions. 59 Base-catalyzed such as KOH transesterification is the favored method when compared to the other methods since it has softer reaction conditions, requires less time to complete, and is less expensive. 60 From the previous studies, it was proved that the oleaginous yeast can produce BD.…”