Biotransformation of algal waste by biological fermentation

Abstract

The garbage of red algae, Gelidium sesquipedale, from a factory after extraction of agar-agar, is indiscriminately discharged into the public environment. Microbiological analyses confirmed that this garbage contains different groups of bacteria whose number is variable: the total aerobic mesophilic flora, 4 x 106 cfu/g; total coliforms, 6 x 105 cfu/g; fecal streptococci, 2 x 102 cfu/g; staphylococci, 180 cfu/g; lactic bacteria, 7 x 103 cfu/g and yeasts 2 x 105 cfu/g. Analyses showed that clostridiums,
salmonellas and faecal coliforms are absent. To treat this garbage of algae, we employed a biological fermentation process using lactic acid bacteria (BL11) and yeast (THE 16). These were isolated and selected for their acidifying and fermentation qualities, respectively. The fermentation resulted in a decrease of pH from 7.4 to 3.75 and a reduction of the different pathogenic groups of bacteria; total coliforms, streptococci and staphylococci. On the other hand, the number of the lactic bacteria increased. Physical and chemical analyses showed that this garbage of algae is rich in mineral elements, proteins, sugars and a small amount fat. This fermentation product can be used as fertilizer and/or integrated in animal feed