Bioconversion of palm oil mill effluent for citric acid production: statistical optimization of fermentation media and time by central composite design

Abstract

A laboratory-scale study was conducted to evaluate the feasibility of using palm oil mill effluent (POME) as a major substrate and other nutrients for maximum production of citric acid using the potential fungal strain Aspergillus niger (A103). Statistical optimization of medium composition (substrate-POME, co-substrates-wheat flour and glucose, and nitrogen source-ammonium nitrate) and fermentation time was carried out by central composite design (CCD) to develop a polynomial regression model through the effects of linear, quadratic, and interaction of the factors. The statistical analysis of the results showed that, in the range studied, ammonium nitrate had no significant effect whereas substrate, co-substrates and fermentation time had significant effects on citric acid production. The optimized medium containing 2% (w/w) of substrate concentration (POME), 4% (w/w) of wheat flour concentration, 4% (w/w) of glucose concentration, 0% (w/v) of ammonium nitrate and 5 days fermentation time gave the maximum predicted citric acid of 5.37 g/l which was found to be 1.5 g/l in the experimental run. The determination of coefficient (R 2 ) from the analysis observed was 0.964, indicating a satisfactory adjustment of the model with the response. The analysis showed that the major substrate POME (P \ 0.05), glucose (P \ 0.01), nutrient (P \ 0.05), and fermentation time (P \ 0.01) was more significant for citric acid production. The bioconversion of POME for citric acid production using optimal conditions showed the higher removal of chemical oxygen demand (82%) with the production of citric acid (5.2 g/l) on the final day of fermentation process (7 days). The pH and biosolids accumulation were observed during the bioconversion process.

A dual response surface optimization methodology for achieving uniform coating thickness in powder coating process

“…The design of experiments is an efficient tool for optimizing the process and product characteristics (Chowdhury & Boby, 2003;Surm et al, 2005;Wang et al, 2008;Bhuiyan, 2011;Sahoo & Sahoo, 2011;Boby, 2013;Kirshna et al, 2013;, Saha & Mandal, 2013;Sahoo, 2014). Since response surfaces need to be fitted for mean and variance of the response variable, a central composite design (CCD) is chosen for experimentation (Alam et al, 2008). The central composite designs have less number of experiments compared to 3 level full factorial experiments.…”

Microwave Assisted Alkaline Pretreatment and Microwave Assisted Enzymatic Hydrolysis of Palm Oil Mill Effluent (POME) for Optimum Fermentable Sugar Yield

“…In this process the rich organic residue is used as a medium where some microbial species grow, consume the organic components and at the same time, produce biomass and other valuable products 17 . These include carotenoid, which canbe further utilized for vitamins A and E (tocopherols) production 18 , citric acid 19 , biohydrogen 20 and bioethanol 21 .…”

“…The containers were tightly capped and stored at 4.0 °C until further use. The POME sample having 4.0% (w/v) of total suspended solid (TSS) was prepared on the basis of material balances 19 .…”

Bioenergy from anaerobic degradation of lipids in palm oil mill effluent

“…Jamal et al (2005) used POME and wheat flour as a medium and screened potential microorganisms for citric acid production and showed that Aspergillus (A 103) produced the highest concentration of citric acid after 2 days of fermentation. Alam et al (2008) investigated the bioconversion of POME, by adding co-substrate (glucose and wheat flour and nitrogen source-ammonium nitrate), for Din et al (2006b) citric acid production under optimal conditions and observed higher removal of chemical oxygen demand (82%) with the production of citric acid (5.2 g/l) on the final day of fermentation process (7 days). Mumtaz et al (2008) generated organic acids with low molecular weight such as acetic acid, propionic acid and butyric acids from partial anaerobic treatment of palm oil mill effluent (POME), using pilot scale filtration and evaporation system.…”