Tepung sagu basah hasil penyediaan secara tradisional kualitasnya cepat berkurang disebabkan karena timbulnya bau masam. Hal ini disebabkan karena adanya asam organik hasil aktivitas mikroorganisme penyebab kemasaman yang terikut selama proses penyediaan. Penelitian ini bertujuan untuk mendapatkan mikroorganisme penyebab kemasaman, menentukan kondisi lingkungan yang terbaik bagi pertumbuhan mikroorganisme penghasil asam organik tinggi sebagai penyebab kemasaman serta menganalisis karakter dan identitas secara polifasik penyebab kemasaman pada tepung sagu basah hasil penyediaan secara tradisional dalam sistematik mikroorganisme. Mikroorganisme penyebab kemasaman dapat diperoleh dengan melakukan isolasi. Sumber isolat diperoleh dari tepung sagu dan lingkungan tempat pengolahan sagu di Desa Maribu dan Jembatan Dua, Jayapura, Papua. Isolat yang didapat diskrining berdasarkan daya hidrolitik amilum, aktivitas amilase dan penghasilan asam organik. Penentuan kondisi lingkungan yang terbaik bagi pertumbuhan dan penghasilan asam organik, dilakukan dengan menumbuhkan isolat dalam medium yang memiliki variasi konsentrasi inokulum, konsentrasi substrat, pH, suhu, agitasi dan waktu inkubasi. Isolat penyebab kemasaman dikarakterisasi dan diidentifikasi menggunakan pendekatan sistematik polifasik yang meliputi pendekatan sistematik numerik-fenetik, pendekatan kemosistematik dengan analisis profil protein ekstrak bebas sel dan pendekatan sistematik molekular dengan menganalisis sequence gen 16S rRNA Selama seminggu pengamatan terhadap tepung sagu basah didapatkan asam organik berupa asam laktat, asetat, propionat, dan butirat, produk cenderung meningkat pada hari ketiga, sedangkan glukosa, gula reduksi dan nilai pH berkurang secara bertahap. Isolasi yang telah dilakukan mendapatkan 268 isolat yang terdiri dari 238 bakteri dan 30 fungi, setelah diskrining berdasarkan daya hidrolitik amilum didapatkan 118 isolat bakteri amilolitik dan 17 isolat fungi amilolitik. Hasil analisis aktivitas amilase mendapatkan 72 isolat memiliki aktivitas amilase lebih dari 24,45 DUN/ml. Skrining berdasarkan asam laktat, asetat, propionat, dan butirat mendapatkan enam isolat bakteri amilolitik yang menghasilkan asam laktat lebih tinggi dibandingkan isolat lainnya, yaitu isolat SPH11, TBSM13, TJ2.12, TBSJ2.4, TM9 dan TM2. Isolat fungi kebanyakan menghasilkan asam laktat lebih rendah dibandingkan isolat bakteri. Pengujian kembali penghasilan asam organik dari isolat terpilih dengan agitasi 100 rpm, menetapkan isolat SPH11, TBSM13 dan TJ2.12 sebagai isolat terpilih. Ketiga isolat dapat menghasilkan asam organik khususnya asam laktat lebih dari 75mg/g tepung sagu secara konsisten. Pada kondisi lingkungan pertumbuhan yang terbaik, isolat terpilih menghasilkan asam organik khususnya asam laktat maksimal sebesar 383 mg/g tepung sagu, dicapai pada hari ke 2 – 3 waktu inkubasi. Hasil karakterisasi dan identifikasi isolat terpilih menggunakan pendekatan polifasik sistematik menunjukkan bahwa isolat SPH11 dan TBSM13 memiliki similaritas fenetik dan hubungan filogenetik dengan Bacillus subtilis, sedangkan isolat TJ2.12 memiliki similaritas fenetik dan hubungan filogenetik dengan Bacillus cereus.

The quality of raw sago starch decrease rapidly caused by organic acid produced by sourness causing microorganism which involved during processing. The aims of this research were to obtain sourness causing microorganism on raw sago starch, to determine the effect of environmental condition on organic acid production, and to study characterization and identification isolates by polyphasic systematic approach. The sourness causing microorganism were obtained by isolation. The sources of microorganism were taken from several samples around of raw sago starch processing traditionally at Maribu and Jembatan Dua villages, Jayapura, Papua. Isolates were then screened based on the hydrolytic amylum activity, amylase activity and organic acid production by Gas Chromatography analysis. The effect of environmental condition for growing and organic acid production were done comprise conditions of inoculums consentration, substrate concentration, pH, temperature, agitation and incubation time. Characterization and identification of sourness causing microorganism were done by polyphasic systematic approach that involved numerical-phenetic systematic on the basic of phenotypic character, chemosystematic based on the character of cell free extract protein profiles analyzis and molecular systematic based on the analysis of 16S rRNA gene sequence. Results the analysis of organic acid, glucose and reduction sugar product on raw starch sago during seven day, resulted in such as lactic, acetic, propionic and butyric acid. Especially lactic acid production increased significantly on the third day analysis but glucose, reduction sugar, and pH decreased gradually day by day. The sourness causing microorganism isolation was done and obtained 268 isolates, that consist of 238 bacteria and 30 fungi. Screening based on the hydrolytic amylum activity were found 118 amylolytic bacteria and 17 amylolytic fungi. Screening based on the amylase activity showed that 72 isolates had amylase activity more than 24,45DUN/ml. Screening of isolates based on the lactic, acetic, propionic, and butyric acid production were obtained six isolates of amylolytic bacteria which produced lactic acid higher than the others, that were isolates SPH11, TBSM13, TJ2.12, TM9, TM2 and TBSJ2.4. Most of the amylolytic fungi had lower organic acid production than bacteri isolates. Reanalyzis of organic acid production these isolates under 100 rpm agitation, were results showed that isolates SPH11, TBSM13 and TJ2.12 as selected isolates. These isolates could produce organic acid, especially lactic acid up to 75mg/g sago starch, consistenly. In the optimal condition organic acid production, especially lactic acid maximum production was obtained at 2-3 days incubation and their production were reached 383 mg/g sago starch. The results of characterization and identification selected isolates by polyphasic systematic approach showed that SPH11 and TBSM13 isolates had high phenetic similarity value and phylogenetic relatedness with Bacillus subtilis and TJ2.12 isolate had similarity and relatedness with Bacillus cereus.

Kata Kunci : Mikroorganisme, kemasaman, dan sagu