Review Article Recent advanced biotechnological strategies to enhance photo-fermentative biohydrogen production by purple non-sulphur bacteria: An overview Ming Foong Tiang a , Muhammad Alif Fitri Hanipa a , Peer Mohamed Abdul a,b,* , Jamaliah M.d. Jahim a,b , Safa Senan Mahmod a , Mohd Sobri Takriff a,b , Chyi-How Lay c,d , Alisara Reungsang e , Shu-Yii Wu c,d a Department of Chemical and Process Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor Darul Ehsan, Malaysia b Research Centre for Sustainable Process Technology (CESPRO), Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, Bandar Baru Bangi, Selangor Darul Ehsan, Malaysia c Department of Chemical Engineering, Feng Chia University, Taichung 40724, Taiwan d Green Energy Development Center, Feng Chia University, Taichung 40724, Taiwan e Department of Biotechnology, Faculty of Technology, Khon Kaen University, Khon Kaen 40002, Thailand highlights  Various biotechnological approaches applied on photo-fermentation are reviewed.  H 2 yield improved by optimisation on medium, abiotic factors and lighting regime.  Novel photoluminating nanomaterials is promising to increase H 2 yield.  Additional H 2 enhancement strategies are recommended for further research. article info Article history: Received 9 December 2019 Received in revised form 23 February 2020 Accepted 5 March 2020 Available online xxx Keywords: Biohydrogen Biotechnological approaches abstract Photo-fermentation seems to be an attractive hydrogen production pathway. However, the light conversion efficiency and photo-hydrogen production of purple non-sulphur bacteria (PNSB) are very low, and hence, various biotechnological approaches are investigated to improve biohydrogen production. This article presents an overview of the advanced biotechnological approaches to enhance the photo-fermentative biohydrogen production. The advancements reviewed include optimisation of the medium, abiotic factors, the lighting regime, immobilisation techniques, application of photoluminating nano- materials, genetic engineering, and other strategies. These approaches show positive re- sults in the enhancement of photo-hydrogen production by PNSB. Some recommendations are suggested for further studies in the enhancement of photo-hydrogen production, such * Corresponding author. Department of Chemical and Process Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor Darul Ehsan, Malaysia. E-mail address: peer@ukm.edu.my (P.M. Abdul). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy xxx (xxxx) xxx https://doi.org/10.1016/j.ijhydene.2020.03.033 0360-3199/© 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Please cite this article as: Tiang MF et al., Recent advanced biotechnological strategies to enhance photo-fermentative biohydrogen production by purple non-sulphur bacteria: An overview, International Journal of Hydrogen Energy, https://doi.org/10.1016/ j.ijhydene.2020.03.033