Altop, I. Coskun, G. Filik, A. Kucukgul, Y.G. Bekiroglu, H. Cayan, E. Gungor, A. Sahin
and G. Erener. 2018. Amino acids, minerals, condensed tannin, and other chemical contents
in olive leaves (Olea europaea L.) processed via solid-state fermentation using selected
Aspergillus niger strains. Cien. Inv. Agr. 45(3): 220-230. The present study aimed to examine
the effects of solid-state fermentation (SSF) using selective A. niger strains on the amino acid,
mineral, condensed tannin, and other chemical contents of olive leaves. The dried samples were
divided into nonfermented (C) and fermented (F) olive leaves, and the latter were fermented by
the following A. niger strains: ATCC® 9142TM (F1), ATCC® 200345TM (F2), ATCC® 52172TM (F3),
and ATCC® 201572TM (F4), with three replicates for each treatment. Group F4 presented the best
results, although all fermented groups generally presented higher performance than C. The total
content of amino acids of the fermented olive leaves increased by 68–209% in comparison to
that of C, while the cellulose content of the fermented olive leaves decreased by 7–25%. The ash,
crude protein (CP), and ether extract (EE) contents increased after fermentation, but the crude
fiber (CF) and nitrogen-free extract (NFE) contents decreased. The content of neutral detergent
fiber (NDF) did not change, but acid detergent fiber (ADF) varied among the groups. The starch
and sugar contents of all fermented groups except F1 also decreased compared to those of C.
The mineral contents increased in all fermented groups, and the condensed tannin content varied
according to the A. niger strain used. Thus, olive leaves fermented with different A. niger strains,
especially F4, seem to have considerable potential as ruminant feed, as they are enriched with
amino acids and minerals and have an improved chemical composition. However, these results
should be supported and validated by animal experiments.