Conversion of Rice straw to caprylic acid-rich microbial oils by oleaginous yeast isolates
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ORIGINAL ARTICLE
Conversion of Rice straw to caprylic acid-rich microbial oils by oleaginous yeast isolates Batul Diwan 1 & Pratima Gupta 1 Received: 6 July 2020 / Revised: 12 September 2020 / Accepted: 25 September 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Incessant research on single cell oils (SCO) has revealed it as a vital sustainable source of rare fatty acids and high value lipids. India is one of the largest global producer of paddy and generates around 130 MT of energy dense lignocellulosic straw, which can be converted into myriad of high-value products. In this context present work demonstrates conversion of rice straw into nutritionally important caprylic-acid rich SCO with concomitant recycling of residual broth for increasing product to effluent discharge ratio along with co-production of singe-cell protein (SCP). Oleaginous yeast isolates Geotrichum candidum NBT-1 and Pichia kudriavzevii NBT-13 employed in the work exhibited co-utilization and simultaneous consumption of glucose and xylose (pre-dominant sugars in lignocellulosic hydrolysates). G. candidum displayed higher lipid titre (5.745 g/L) and biomass concentration (14.88 g/L) in 1:1 combination of non-detoxified rice straw liquid hydrolysate (NDLH) and synthetic media compared with titre (4.32 g/L) and biomass concentration (8.61 g/L) obtained in synthetic media (control). P. kudriavzevii could not endure NDLH and kinetics revealed initiation of lipid-turnover after 168th h. Residual broth was 100% recycled without fresh carbon supplementation resulting in additional lipid titre and yield of 2.45 g/L and 8.12% from G. candidum, in two consecutive fermentations. Defatted biomass from both isolates was 48.66 (NBT-1) and 37.11% (NBT-13) protein rich, a suitable SCP candidate as food or feed supplement. Derived SCO were 70–90% predominant in medium chain fatty acid-caprylic acid, recognized for its ever-increasing nutraceutical and medical benefits with concomitant production of SCP biomass. Keywords Lignocellulosic rice straw biomass . Non-detoxified liquid hydrolysate (NDLH) . Broth recycle . Medium chain fatty acid rich oils . Oleaginous G. candidum and P. kudriavzevii
1 Introduction Exploding world population and technological advancements is increasing urbanization and industrialisation, which is exponentially increasing both need of resources and generation of degradable and nondegradable wastes of solid, liquid and gaseous nature. World bank reports suggest this waste generation would reach to 2.5–3.5 billion tons by 2030 and 2050, respectively. Of the agricultural wastes generated, majority are of lignocellulosic nature. Lignocellulosic biomass with more than 15 × 1010 tons of world annual production are amongst
* Pratima Gupta [email protected]; [email protected] Batul Diwan [email protected]; [email protected] 1
Department of Biotechnology, National Institute of Technology, GE Road, Raipur 492010, India
the most ubiquitous natural material [1]. The presence of strongly inte
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