Cellulose, hemicellulose and lignin are the main com­ponents found in lignocellulosic raw materials and the corresponding composition is dependent on the biomass resource. Production of sugar-rich hydrolysates from lignocellulosic biomass requires treatment with com­bined thermochemical treatment and enzymatic hydro­lysis. Previous studies on utilization of lignocellulosic resources have focused on hydrolysis of cellulose and hemicellulose fractions to simple sugars for microbial fermentation mainly aiming to bioethanol production. Nonetheless, given the interest arising in biopolymers production, bioethanol production could be combined with PHA production. Cellulose could be utilized for the production of bioethanol, while sugars from hemi — cellulose could be utilized for the production of PHAs. In this way, conventional processes employed for the production of bioethanol from lignocellulosic biomass could be upgraded into advanced biorefinery concepts.

Silva et al. (2004) screened 55 strains as potential PHB producers from xylose and identified Burkholderia sac — chari IPT 101 and Burkholderia cepacia IPT 048 that were subsequently evaluated via cultivations on xylose and bagasse hydrolysates. Intracellular PHB content reached 62% and 53% for the two strains, respectively, when grown on bagasse hydrolysates. Keenan et al. (2006) utilized detoxified hemicellulose hydrolysates from lignocellulosic resources for the production of P(3HB — co-3HV) with B. cepacia through supplementation with levulinic acid (0.25—0.5%) to achieve a P(3HB-co-3HV) concentration of 2 g/l, a P(3HB-co-3HV) content of 40% (w/w) and 3HV composition of 16—52 mol%. When xylose and levulinic acid were used in microbial biocon­versions with B. cepacia, the P(3HB-co-3HV) concentra­tion and 3HV composition achieved were up to 4.2 g/l and 61 mol%, respectively. Sugarcane bagasse hydroly­sates were evaluated for PHA synthesis via fermentation of R. eutropha (Yu and Stahl, 2008). The effect of inoc­ulum concentration, dilution of hydrolysate and imple­mentation of an adapted strain was studied regarding PHA accumulation, which reached up to 57% (w/w) polymer content. PHB was the major polymer accumu­lated, whereas copolymers could be also produced that presented high ductility.

PHA production could be incorporated in existing bioethanol production facilities from both sugar cane in Brazil and cereals, such as wheat and corn, in other countries worldwide. Sugar cane utilization for bio­ethanol production generates significant quantities of bagasse, a lignocellulosic raw material that could be used for combined production of ethanol from cellulose and PHAs from hemicellulose sugars (mainly xylose). Integration of PHA production in existing cereal-based facilities used for bioethanol production could be achieved by incorporating straw utilization as raw mate­rial for combined production of bioethanol and PHAs. Such integrated biorefinery concepts could improve the sustainability of first-generation bioethanol produc­tion plants.