Epsilon Archive for Student Projects

Abstract

Ethanol for automotive purposes is an issue much debated and researchers disagree about the benefits of bioethanol. Converting energy-rich crops into ethanol suitable as motor fuel is a complex process and continuous development and improvements of processes and material used are important steps in the work of developing environmental friendly fuels. Grain is usually preserved by drying which consumes a lot of energy. Alternative storage of high-moisture grain in airtight storage systems reduce the energy required to produce bioethanol and studies have also shown that ethanol yields are increased more than 10% in ethanol fermentations of moist grain compared to dry. Airtight storage is often not perfectly airtight so biocontrol agents are necessary in order to preserve the grain. The yeast Pichia anomala has anti-microbial activity and inhibits mould growth in airtight stored moist grain with some air leakage and is therefore an attractive alternative for biocontrol.

Starch has to be degraded by enzymes into fermentable sugars before it can be fermented into ethanol. Storing high-moisture grain improves enzymatic degradation which results in higher ethanol yields and the aim of this study was to investigate if ethanol yields could be increased further by pre-treating the grain with amylase producing Lactobacillus plantarum strains in combination with P. anomala J121. Amylase is an enzyme that degrades starch into sugar units and pre-treating grain with bacteria that has amylase activity might have a positive effect on glucose concentrations in grain before and after starch is enzymatically degraded and ultimately result in increased ethanol yields. Also, lactic acid bacteria have been observed to have antifungal activity.

Amylase producing L. plantarum strains Amy 1 to 7 were screened for their ability to degrade starch and for possible antifungal activity. No inhibiting activity against P. anomala J121 or Penicillium roqueforti J9 was detected. L. plantarum Amy 1 to 7 did inhibit growth of Fusarium culmorium J617. L. plantarum Amy 1, was used in a two months storage study to investigate how ethanol yields are affected by microbial pretreatment during storage. Grain was inoculated with L. plantarum Amy 1 or P. anomala J121 alone or a combination of the two and fermentations were performed on the grain after one month and two months of storage. Inoculation with L. plantarum Amy 1 did not increase ethanol yields, but slightly higher yields were observed in grain pretreated with P. anomala J121. Two different moisture contents of the grain were used in the study; 25% and 40%. Increased ethanol production rates were observed in the wetter grain but final ethanol yields were similar in both moisture contents. Earlier findings that ethanol yields are increased in fermentations of grain stored moist was confirmed. To study if pretreatment with L. plantarum Amy 1 can increase storage stability of moist grain a storage study with P. roqueforti J9 was performed and also to ensure that any glucose released during pretreatment does not increase mould growth. Increased storage stability by inoculating grain with L. plantarum Amy 1 could not be concluded from this study. However, no increased mould growth was observed in grain treated with L. plantarum Amy 1.