This study evaluated the modification of bioplastics production by various ratios of sorghum starch and cellulose from red seaweed eucheuma spinossum, and the use of glycerol as plasticizer and sorghum stalks as filler. Solid-liquid matrix transition should be far over the operating temperature of gelatinization and extracted at 95 o C in order to avoid the loss of conductivity. The analyzed variables were starch and cellulose seaweed eucheuma spinossum and the addition of variation of filler. Sorghum stalk addition expected to affect the mechanical and physical properties of bioplastics. A thin sheet of plastic (plastic film) was obtained as results that have been tested mechanically to obtain the best condition for the formulation of starchcellulose 8.5:1.5 (g/g). From the result of morphological studies, the fillers in the mixture composites were more randomly in each product and the addition of filler can increase mechanical properties of bioplastics. Chemical modification had a major effect on the mechanical properties. The phenomena of degradation and thermo-plasticization were visible by chemical changes observed in FTIR spectrum results.Keywords: bioplastics, sorghums starch, cellulose, filler. AbstrakPenelitian ini mengevaluasi modifikasi produksi bioplastik dengan beragam rasio pati sorgum dan selulosa dari rumput laut eucheuma spinosum, penggunaan gliserol sebagai plasticizer dan batang sorgum sebagai pengisi. Transisi matriks padat-cair harus jauh di atas suhu operasi gelatinisasi dan diekstraksi pada 95 o C untuk menghindari hilangnya konduktivitas. Variabel yang dianalisis adalah pati dan selulosa rumput laut eucheuma spinosum dan penambahan pengisi batang sorgum, diduga dapat mempengaruhi sifat mekanik dan fisik bioplastik. Lembaran tipis plastik (film plastik) diperoleh sebagai hasil yang telah diuji mekanik untuk mendapatkan kondisi terbaik pati-selulosa 8,5: 1,5 (g/g). Berdasarkan hasil uji morfologi, pengisi dalam komposit campuran lebih acak pada setiap produk, dan penambahan pengisi dapat meningkatkan sifat mekanik bioplastik. Modifikasi kimia berpengaruh besar pada sifat mekanik. Fenomena degradasi dan thermoplastisasi terlihat pada perubahan kimia yang dapat diamati pada spektrum hasil uji FTIR.