Utilization of stillages from bioethanol production from various substrates

Abstract

Stillage is a main by-product of the bioethanol industry and, depending on the origin of substrates for bioethanol production, it can be a significant pollutant affecting the profitability of bioethanol production. Directing the stillage towards the production of bio-based chemicals or high-quality feed is a preferred stra- tegy. In this paper, a complete utilization of stillages of different origins was assessed. Thin stillages from bioethanol production from molasses, wasted bread and corn were chemically characterized, evaluated and compared as substrates for lactic acid (LA) and probiotic biomass production by Lactobacil- lus rhamnosus ATCC 7469, while solid fractions of wasted bread and corn stil- lages were analyzed for feed. The impact of pH control using CaCO 3 or NaOH was also examined, both in terms of LA production and valorization of the remains generated in each process.A maximal LA productivity of 1.14 g/(L h) was obtained on thin wasted bread stillage with pH control by NaOH while the number of viable probiotic bacterial cells was above 109 CFU/mL. The com- position of the solid fraction of the wasted bread stillage was complementary with the needs of monogastric animals, while the solid fraction of corn stillage was more adequate for the nutritional requirements of ruminants.

Džibra je najznačajniji otpadni ili sporedni proizvod industrije bioetanola. U zavisnosti od porekla supstrata koji se koriste u proizvodnji bioetanola, može biti značajan zagađivač, pa utiče na profitabilnost proizvodnje bioetanola. Upotreba džibre u biotehnološkim postupcima proizvodnje hemikalija ili visoko vredne stočne hrane je poželjna strategija za smanjenje negativnih efekata džibre na životnu sredinu i profitabilnost proizvodn je bioetanola. U ovom radu je analizirana mogućnost kompletnog iskorišćenja džibre. Tečne džibre iz proizvodnje bioetanola na melasi, otpadnom hlebu i kukuruzu su hemijski okarakterisane i upoređene kao supstrati za proizvodnju mlečne kiseline (MK) i probiotske biomase soja Lactobacillus rhamnosus ATCC 7469, dok je čvrsti ostatak hlebne i kukuruzne džibre analiziran kao hrana za životinje. Takođe je ispitan uticaj pH kontrole pomoću CaCO3 ili NaOH sa aspekta proizvodnje MK i sa aspekta iskorišćenja ostataka iz oba procesa. Maksimalna produktivnost MK od 1,14 g/(L h) je dobijena na tečnoj džibri iz otpadnog hleba sa pH kontorolom pomoću NaOH, dok je broj živih pro- biotskih bakterija bio preko 10 9 CFU/mL. Rezultati su pokazali da je sastav čvrste frak- cije otpadne hlebne džibre komplementaran sa potrebama monogastričnih životinja, dok sastav čvrste frakcije kukuruzne džibre više odgovara nutritivnim potrebama preživara.