Property, plant and equipment, net (Details) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Cost
Construction in progress	$ 715,188	$ 1,678,961
Furniture, fixtures and office equipment	4,025,635	3,882,594
Leasehold improvement	5,865,909	4,092,668
Machinery and equipment	27,526,572	29,295,041
Motor vehicles	1,496,628	1,643,173
Building	21,797,158	23,046,056
Property, plant and equipment, cost	61,427,090	63,638,493
Less: accumulated depreciation	17,922,099	16,174,307
Property, plant and equipment, net	$ 43,504,991	$ 47,464,186