Utilization of agricultural residues for poly(3-hydroxybutyrate) production by Halomonas boliviensis LC1

Abstract

Aims: Utilization of cheap and readily available agricultural residues as cheap carbon sources for poly(3‐hydroxybutyrate) (PHB) production by Halomonas boliviensis. Methods and Results: Wheat bran was hydrolysed by a crude enzyme preparation from Aspergillus oryzae NM1 to provide a mixture of reducing sugars composed mainly of glucose, mannose, xylose and arabinose. Growth of H. boliviensis using a mixture of glucose (0·75% w/v) and xylose (0·25% w/v) in the medium led to a PHB content and concentration of 45 wt% and 1 g l−1, respectively, after 30 h. A similar PHB concentration was attained when H. boliviensis was grown on wheat bran hydrolysate but with a lower PHB content, 34 wt%. In a batch cultivation mode in a fermentor, using 1·8% (w/v) reducing sugars, the maximum PHB accumulation by H. boliviensis was attained in 20 h, but was reduced to about 30 wt%. By adding butyric acid (0·8% v/v), sodium acetate (0·8% w/v) and decreasing the reducing sugars concentration to 1·0% w/v in the medium, PHB accumulation and concentration were increased to 50 wt% and 4 g l−1, respectively, after 20 h. Butyric acid and sodium acetate for PHB production could also be provided by anaerobic digestion of solid potato waste. Conclusions: Cheap and readily available agricultural residues can be used as substrates to produce PHB. The production of PHB by H. boliviensis using wheat bran hydrolysate as source of carbon is expected to reduce the production cost and motivates further studies. Significance and Impact of the Study: Large‐scale commercial utilization of PHB is mainly hampered by its high production cost. Carbon source for PHB production accounts up to 50% of the total production costs. Thus, the use of waste agricultural residues can substantially reduce the substrate cost (and in turn even provide value to the waste), and can downsize the production costs. This improves the market competitiveness. Studies on PHB production by moderate halophiles were recently initiated with H. boliviensis and findings show that it has potential for commercial exploitation. PHB production by H. boliviensis using wheat bran and potato waste is hence interesting.

Agrowaste-based Polyhydroxyalkanoate (PHA) production using hydrolytic potential of Bacillus thuringiensis IAM 12077

“…This could be attributed to these substrates being rich in protein, or other nutrients as well that triggered the growth phase instead of nutrient depletion. Similar observations were made by Van-Thuoc et al (2007) and Ramadas et al (2009) wherein wheat bran and cassava bagasse supported good growth but low PHB accumulation. There was a positive correlation between the amount of reducing sugar released [data not shown] by acid hydrolysis of the substrates with the PHB yield obtained (r = 0.70538).…”

“…However, 4 g/L PHB has been obtained from R. eutropha using hydrolyzed starch. Van-Thuoc et al (2007) reported that in order to use the agroindustrial residues as fermentation substrates, these should be subjected to hydrolysis for the release of easily metabolizable sugars. Acid and enzymatic methods are the two main reported methods for the hydrolysis, but acid hydrolysis requires more energy for heating and is relatively difficult to control.…”

Bioconversion of Commercial and Waste Glycerol into Value-Added Polyhydroxyalkanoates by Bacterial Strains

“…The genus Halomonas is well known for being able to synthetize PHA, many species in this family assimilate several different carbon sources that can be obtained from waste residues or by-products and has the potential to be used as inexpensive raw materials for PHA production [20]. According to [21] Halomonas boliviensis has been already reported to produce polyhydroxyalkanoates from several different carbon sources, like glucose, xylose, sucrose, maltooligosacharides, sodium acetate and butyric acid. Currently alternatives ways for improving PHA production are being investigated by other researchers with representatives of genus Halomonas by using less expensive substrates and scaling-up fermentation.…”

Exploring biodegradable polymer production from marine microbes

“…A wide range of industrial by-products has been used for PHAs production like agricultural, household waste materials, sugars, lignocellulosic raw materials, fats, and oils. Among those, extensive research is focused on wastes, sucrose [108], starch [109], glucose [110][111][112], soy molasses and hydrolysed soy [113,114], sugar cane molasses [115][116][117], waste rapeseed oil [118,119], sunflower meal hydrolysates [120], glycerol [121,122], rice bran and corn starch [74], lard oil, butter oil, and coconut oil [123], palm oil and its products [124], sugar beet molasses [125], spent palm oil [126], cellulose and cellulose hydrolysates [127], sugarcane bagasse hydrolysates [128,129], casein hydrolysate [130], rapeseed meal hydrolysates [131], triacylglycerides (TAG) [132], sugarcane liquor [133], acetic acid [111,134], corn steep liquor [135], fish peptone medium [136], galactose, mannose and rhamnose [137], cheese whey and hydrolysed whey [115,138,139], urea [117], oil [124], wheat based biorefinery [140,141], xylose [128], arabinose …”