초록
<P><B>Highlights</B></P><P>► Economical & sustainable citric acid (CA) production using apple industry waste. ► Economy use of negative cost agro-industrial wastes. ► To met the rising demand of CA in many advanced applications in food & biomedicines. ► To lessen the environmental hazards caused by the disposal of agro-industrial wastes. ► Environmental capture of waste carbon leading to mitigation of climate change.</P> <P><B>Abstract</B></P><P>Ever-growing demand for citric acid (CA) and urgent need for alternative sources has served as a driving force for workers to search for novel and economical substrates. Submerged fermentation was conducted using apple (<I>Malus domestica</I>) pomace ultrafiltration sludge as an inexpensive substrate for CA bioproduction, using <I>Aspergillus niger</I> NRRL567. The crucial parameters, such as total suspended solids and inducer concentration, were optimised by response surface methodology for higher CA production. The optimal CA concentrations of 44.9g/100g and 37.9g/100g dry substrate were obtained with 25g/l of initial total solids and 3% (v/v) methanol and 25g/l of total solids and 3% (v/v) ethanol concentration, respectively, after the 144h of fermentation. Results indicated that total solids concentration, and methanol as an inducer, were effective with respect to higher CA yield and also indicated the possibility of using apple pomace sludge as a potential substrate for economical production of CA.</P>