Antagonistic Activity of Indigenous Yeast from Fermented Coffee Beans against Aspergillus ochraceus

ANASTASIA CELESTINE, Dr. Dian Anggraini S., STP., MP., M.Eng.; Dr.nat.techn. F.M.C. Sigit Setyabudi, STP, M.P.

2021 | Skripsi | S1 TEKNOLOGI PANGAN DAN HASIL PERTANIAN

Kontaminasi Aspergillus ochraceus sebagai salah satu penghasil utama OTA selama proses fermentasi kopi telah menjadi salah satu hambatan terbesar bagi produk kopi di negara-negara tropis. Kapang (yeast) lokal memiliki potensi yang besar sebagai agen pengontrol cendawan penghasil okratoksin, serta memiliki peran menguntungkan untuk proses fermentasi kopi. Penelitian ini bertujuan untuk mengidentifikasi kapang lokal yang diisolasi dari biji kopi terfermentasi, yang sekaligus diamati kemampuan pektinolitik dan aktivitas antagonistiknya terhadap Aspergillus ochraceus. Identifikasi spesies kapang dilakukan menggunakan alat API 20C Aux, tiga isolate kapang teridentifikasi sebagai Candida sphaerica (WBY1), Candida famata (WBY2), dan Candida pelliculosa (WBY3). Dua dari tiga isolat kapang (Candida sphaerica and Candida famata) menunjukkan aktivitas pektinolitik. Sementara itu, dua isolat cendawan (PJ1, diprediksi sebagai A. ochraceus dari biji kopi terfermentasi; A.Oc., kontrol positif) diuji kemampuannya dalam menghasilkan OTA menggunakan alat ELISA, dimana menunjukkan produksi OTA lebih tinggi pada MEA daripada agar YES. Selanjutnya, seluruh isolate kapang mampu sedikit mengurangi diameter dan penghambatan produksi spora pada A. ochraceus setelah lima hari diinkubasi. Namun, tidak teramati pengurangan kadar OTA. Maka, optimisasi metode kokultivasi menggunakan variasi jumlah inokulasi dan tingkat konsentrasi sel kapang perlu dilakukan untuk memeroleh pengamatan lebih jelas terhadap pengaruh aktivitas antagonistik yang sudah ditunjukkan oleh isolate kapang di penelitian ini. Identifikasi lebih lanjut seluruh isolat pada tingkat strain dan pengamatan spesifik terhadap mekanisme pektinolitik tiap isolat kapang juga perlu dilakukan untuk pengembangan selanjutnya sebagai kultur starter fermentasi kopi.

Contamination by Aspergillus ochraceus as one of the major OTA producer during the coffee fermentation process has been one of biggest market constraints for coffee products in tropical countries. Indigenous yeasts have great potential to be control agents of ochratoxigenic fungi, while having advantageous role in coffee fermentation. This research aims for identifying the indigenous yeasts isolated from fermented coffee beans, which also being observed for their pectinolytic activity and antagonistic activity against Aspergillus ochraceus. The identification of yeast species was conducted using API 20C Aux kit, three yeast isolates were identified as Candida sphaerica (WBY1), Candida famata (WBY2), and Candida pelliculosa (WBY3). Two out of three yeasts (Candida sphaerica and Candida famata) showed pectinolytic activity. Meanwhile, two fungi isolates (PJ1, predicted as A. ochraceus from fermented coffee beans; A.Oc., positive control) were assessed for their OTA-producing ability using ELISA kit, which showed higher OTA production in MEA than YES Agar. Furthermore, all yeast isolates showed little colony reduction and sporulation inhibition on A. ochraceus after five days of incubation. However, no OTA reduction was observed. Therefore, optimization of co-cultivation method using variation of yeast cell concentrations and inoculation amount was necessary to observe more significant effect of antagonistic activity which has been shown by the yeasts in this research. Further identification of isolates in strain level and observation of specific pectinolytic mechanism by each yeast should also be conducted for future developments as starter culture in coffee fermentation.

Kata Kunci : Antagonistic activity, yeast, ochratoxigenic fungi, Aspergillus ochraceus, pectinolytic activity, sporulation and growth inhibition, coffee fermentation