A combination of evaporation and chemical preservation for long‐term storage of fresh sweet sorghum juice and subsequent bioethanol production

Abstract

Evaporation and chemical preservation were combined for long‐term storage of sweet sorghum juice (SSJ). The preserved SSJ was further used as substrate for ethanol fermentation. Different chemicals including hydrogen peroxide, sodium hypochlorite, sodium benzoate, and methyl paraben were used as co‐preservatives and were added into concentrated SSJ that contains ~40% (w/v) of sugars. The effects of chemical preservatives on sugar storage and ethanol fermentation were compared. The results showed that methyl paraben has better sugar preservation ability and an acceptable yeast toxicity when compared with other chemicals. The addition of methyl paraben in concentrated SSJ was further evaluated and optimized. By adding 0.4 g/L of methyl paraben, 95.1% of fermentable sugars in SSJ were preserved after a 90‐day preservation at room temperature. Ethanol concentration of 121.1 ± 4.6 g/L with a yield of 0.45 ± 0.02 g/g was obtained using the preserved SSJ in batch fermentation. Practical applications Ethanol production by sugar‐containing juices is of interest because it is more effective, cheaper, and easier than the lignocellulosic routes. However, the commercialization of the bioethanol plants that uses the sweet sorghum juice as a substrate has long suffered from the deterioration of sugars. As a consequence, the ethanol fermentation process is limited by the short intermittent substrate supplementation in order to satisfy the harvest of the fresh stalks. This work comes up with a novel “evaporation+chemical” preservation method. The synergistic effect of high concentration of sugars and methyl paraben preservative showed inspiring sugar preservation results. Most of the sugars in the sweet sorghum juice were preserved for at least 90 days at room temperature and can be used for ethanol fermentation effectively. The continuity of fermentation can be significantly improved, which showed promising results in year‐round operations.

Enhancement of Enduracidin Accumulation from Sweet Sorghum Juice via Alleviation of Oxidative Damage in Streptomyces Fungicidicus M30

“…Nevertheless, the biotechnology utilization process is still not commercialized, mainly because of short-term preservation period of sugars in sweet sorghum juice [29]. Interestingly, a combination of evaporation (400 g/L of sugar concentration) and chemical preservation (0.4 g/L of methyl paraben) for long-term storage of fresh SSJ has been developed, and only 5.0% of fermentable sugars in SSJ were consumed after a 90-day preservation at room temperature [11], making SSJ more attractive as low-cost alternative substrate for bio-chemicals production. In this case, chemical preservative, such as methyl paraben, was used to extend the storage period of SSJ, but methyl paraben had a broad spectrum antibacterial agent [30], which could in uence the microbial metabolism and metabolite accumulation.…”

“…As a C4 crop, sweet sorghum contains rich fermentable sugars in its stems (such as sucrose, glucose and fructose) and a variety of cultivars and growing characteristics such as high biomass yield and rapid growth, which make it an attractive feedstock for value-added biochemical production. A number of fuels and bio-chemicals have been successfully produced using sweet sorghum juice (SSJ) as feedstocks [7][8][9][10][11][12]. In a previous study, we have shown that SSJ was the preferred feedstock for enduracidin production with approximately equivalent e ciency to that of glucose, and S. fungicidicus M30 can also produce 1.01 ± 0.05 g/L of enduracidin via clari cated SSJ and fed-batch strategy [13].…”

Conversion sweet sorghum biomass to produce value-added products

“…For instance, at the pre-flowering stage, the maximum sugar concentration can reach 16–23°Brix [ 8 ]. Compared with cellulosic hydrolysates as a feedstock, bio-chemical production from sweet sorghum juice is easier and cheaper for economic production, since it does not need the costly processes of pretreatment and detoxification [ 22 ]. Using sweet sorghum juice as a feedstock, two technological methods have been conducted as follows.…”

“…Currently, the biggest challenge for industrialization utilization of sweet sorghum juice could be attributed to the short‐term preservation period of fermentable sugars because of the contaminations by other microbes. To avoid the problem, several strategies have been tried [ 22 , 26 , 27 ]. Interestingly, long‐term storage of fresh sweet sorghum juice (about a 90‐day preservation at room temperature) has been developed based on the combination of evaporation and chemical preservation, showing only 5.0% fermentable sugar loss, and finally Saccharomyces cerevisiae M 3013 can produce 121.1 ± 4.6 g/L ethanol with a yield of 0.45 ± 0.02 g/g using the sweet sorghum juice with 90 days of preservation as a feedstock [ 22 ].…”

Production and Purification of l-lactic Acid in Lab and Pilot Scales Using Sweet Sorghum Juice

“…Sweet sorghum is the most utilized crop for bio-based chemicals production in China, but it has been also recognized worldwide as an interesting feedstock [11]. It has already been used for the production of bioethanol or in two stage ethanol-methane production [12,13] and it is one of the most common feedstocks for bio-butanol production [14]. Sweet sorghum juice (SSJ) has also been used for the fermentative production of l-lactic acid.…”