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Summary Submerged citric acid (CA) bioproduction was carried out by Aspergillus niger NRRL-567 using various industrial wastes, such as brewery spent liquid (BSL), lactoserum and starch industry water sludge. CA bioproduction was carried out by varying the temperature (25-35 °C), pH (3-5), addition of inducers, incubation time and supplementation with different proportions of apple pomace ultrafiltration sludge (APS). The results indicated that under the best conditions with 3% (v/v) methanol, the optimal concentration of 11.34 g L−1 CA was recorded using BSL at pH 3.5 and temperature 30 °C after 120-h incubation period. Supplementation of methanol resulted in an increase of 56% CA production. Meanwhile, under similar conditions, higher concentration of 18.34 g L−1 CA was reported with the supplementation of BSL with 40% (v/v) APS having suspended solids concentration of 30 g L−1. The present study demonstrated the potential of BSL supplemented with APS as an alternative cheap substrate for CA fermentation. [ABSTRACT FROM AUTHOR]

The effect of different types of agitation (i) continuous agitation ( C); (ii) continuous, discontinuous, continuous agitation ( C/ D/ C); (iii) discontinuous, continuous, discontinuous agitation ( D/ C/ D) and aeration (0.87, 1.25, 1.66 vvm) on ligninolytic enzyme production and polyphenolic compounds extraction by solid-state cultures of Phanerochaete chrysosporium BKM- F-1767 was investigated. Higher production of manganese peroxidase ( Mn P) (1690.3 ± 87.6), lignin peroxidase ( Li P) (387.9 ± 14.3) and laccase (898.9 ± 53.3 U gds−1) and liberation of total polyphenolics (ranging from 12.22 ± 1.1 to 30.12 ± 0.88 mg gallic acid equivalents per gram DW) was obtained after 195, 147, 219 and 204 h of fermentation, respectively, using 1.66 vvm as airflow and ( C/ D/ C) agitation mode. Maximal enzyme production and total polyphenolic content were influenced by aeration, and higher values were obtained using 1.66 vvm as airflow rate, followed by 1.25 and 0.83 vvm, respectively. They were also influenced by agitation, and maximal values were obtained using C/ D/ C, followed by D/ C/ D and continuous agitation, respectively. The agitation modes influenced the production of ligninolytic enzymes and simultaneous extraction of polyphenols. [ABSTRACT FROM AUTHOR]